SEHI

Sheikh Technical Veterinary School (STVS)

Mapping of Rift valley fever risk areas in Somaliland

A mini thesis submitted in a partial fulfilment for requirements for the award of Diploma in Livestock Health Sciences (DLH) of sheikh technical veterinary school.

BY: Osman Abdulahi Farah

Roll number: STVS/0087

Supervisor Dr. Ismail Kane

July 2011

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DECLARATION

I, Osman Abdulahi Farah declare that the work presented here is my original work, and has

not appeared anywhere else in any other form except for the references made from other

published works.

Students Name : ………………………………………………………………..

Signature: …………………………………………………………….................

Supervisor signature: …………………………………………………

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ACKNOWLEDGEMENT

In the name of Allah, the Most Gracious and the Most Merciful Alhamdulillah, all praises to

Allah for the strengths and His blessing in completing this thesis. Special appreciation goes to

my supervisor, Dr Ismail Kane, for his supervision and constant support. His invaluable help

of constructive comments and suggestions throughout the thesis works have contributed to

the success of this research. Not forgotten, my appreciation to my Tutor of information

technology Mr. Mohamed Aden Ahmed and Abdirahman Bare Dubad for their support and

knowledge regarding this topic.

I would like to express my appreciation to the Dean of studies in (STVS) Dr Abdulahi

Sheikh Mohamed Nour, H.O.D in STVS officer, Dr Ibrahim Osman Suleiman, principal of

STVS Dr. Thomas Bazarusanga, all my Tutors in STVS for their support during my

education in veterinary and STVS administration for their encouragements.

Sincere thanks to all my fellow students in STVS like Hassan Adam Hussein for his

technical support and my unforgettable class mates for their kindness and moral support

during my study.

Last but not least, my deepest gratitude goes to my beloved parents; Mr. Abdullah Farah

Xamse and Mrs. Zahra Mohamud Hussein and also to my sisters and brothers for their

endless love, prayers and encouragement.

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CONTENTS PAGE NO

Cover page…………………………………………………………………………………...1

Declaration------------------------------------------------------------------------------------------------2

Acknowledgement----------------------------------------------------------------------------------------3

Table of Contents-----------------------------------------------------------------------------------------4

CHAMPTER ONE INTRODUCTION AND LITERATURE REVIEW................................6

1.1 General Introduction ………………………………………………..………………….....61.2 Literature review of RFV disease……………………………………………………….....81.2.1 Disease definition…………………………………………………………………......91.2.2 A aetiology of the Rift Valley fever………………………………………………......91.2.3 Epidemiology of the Rift Valley Fever…………………………………….. ……......91.2.4 Pathogenesis………………………………………………………………………......91.2.5 Implication of human healthy………………………………………………………....91.2.6 Geographic distribution of Rift valley Fever………………………………………...101.2.7 Environmental conditions…………………………………………………………....111.2.8 Modes of transmission…………………………………………………………….....121.2.9 Clinical signs of Rift Valley fever…………………………………………………....131.2.9.1 Sheep and Cattle…………..…………………………………………………….…....141.2.9.2 Goat…………………………………………………………………….....................141.2.9.3 Human………………………………………………………………………...……...141.2.9.4 Camel………………………………………………………………………………...151.2.10 Pathology of RVF………………………………………………………………….....161.2.11 Diagnosis and Vaccination………………………………………………………...…171.2.12 Control………………………………………………………………….…………....181.2.13 Mapping of RFV disease……………………………………………………….........191.3. General and specific objectives……………………………………………………..…..19

1.3.1 General objectives……………………………………………………………………...19

1.3.2 Specific Objectives…………………………………………………………...…...........19

CHAPTER TWO METHOD AND MATERIAL....................................................................20

2.1 Data collection....................................................................................................................20

2.2 Data Management and Analysis.........................................................................................20

2.3 Administrative structure of Somaliland.............................................................................20

2.4 laboratory techniques.........................................................................................................22

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2.5 Description of study of study area……………………………………………………….22

3.5.1 Climate geography……………………………………………………………………..23

CHAPTER THREE RESULTS.............................................................................................. 24

CHAPTER FOUR DISCUSSION...........................................................................................25

4.1discussion……………………………………………………………………………........25

CHAPTER FIVE CONCLUSION AND RECOMMEDATION............................................28

5.1 Conclusion………………………………………………………………………………..28

5.2 Recommendation…………………………………………………………………………28

ANNEX ONE REFERENCE ……………………………………………….…………........29

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CHAPTER ONE: GENERAL INTRODUCTION AND LITERATURE REVIEW

1.1 introduction

Rift Valley fever (RVF) is one of the most serious trans-boundary animal diseases. It is a

mosquito-borne viral disease, which causes periodic severe epidemics, principally involving

ruminant animals. RVF is also an important zoonosis and one of the significant acute

haemorrhagic fevers affecting human beings and animals (Shoemaker 2002).

The disease is most severe in sheep, cattle, goat, producing high mortality in newborn

animals and abortion in pregnant animals, it is a zoonosis and human become infected from

contact with tissue of infected animals or mosquito bite.(Shoemaker 2002).

RVF activity reported in 25 African countries (Meganand Bailey, 1989; Peters and Lin-

thicum, 1994).The disease results in high mortality and abor-tions in domestic animals, and a

mortality rate of less than 1 percent among humans (Peters and Linthicum, 1994).

Rift Valley Fever was first recorded in South Africa in 1950-51 in the Northern Cape,

Western Free State and the then Southern Transvaal. It started in the Western Free State in

December 1950 and it continued until April 1951.

The first documented epizootic of RVF occurred on a farm in 1930-1931 near Lake

Naivasha, Kenya with high mortality among sheep (Daubney et al., 1931).The name Rift

Valley refers to the location of the first isolation of the virus in the Rift Valley region of

Kenya dominated by Savanna grasslands. Their findings showed that the disease was vector

borne, transmitted by a variety of mosquito species, and affected both domestic animals and

humans.

During 1977 ,epidemic occurred along the Nile delta and Valley in Egypt, causing an

unprecedented number of human infections and deaths, as well as numerous abortion in sheep

and goat and some loses in goats, and camels,

In September 2000, RVF broke out simultaneously in Jizan province in South West Arabian

ad joint Yemen (Shoemaker 2002)

A recent outbreak in Saudi Arabia and Yemen, (September through November 2000)

documents for the first time the occurrence of the RVF virus outside of continental Africa

(WHO, 2000). And as the main exporting country of livestock from Somalia, the first 6

suspected of this disease was Somalia as result of outbreak in yemen and Suadi Arabia

animals exported to Somalia was boycotted resulting overstocking and depreciation of

animal price contribute to household economy decrease.

And the diseases come in to being in Somalia as a result of the events which coincided with

El-Niño in 1997 –1998 in the region. Targeted surveillance in sero-positive sites in central

and south Somalia was carried out by the Somali component of the PACE project in 2004.

Following the massive RVF epizootic in north-eastern Kenya in 2006 – 2007, around a 100

human cases were suspected and one confirmed in southern Somalia (WHO/CDC), in parallel

with reports of high abortion rates in the small ruminants. As from January 2007, a targeted

survey was initiated in the Afmadow District (South) SAHSP (Somali Animal Health Service

Project 2007) .

The outbreaks were confined to north-eastern Kenya and the southern regions of Somalia and

no cases were reported in northern Somalia (FAO, 1998; WHO, 1998). However, considering

the frequent movement of livestock from south and central Somalia to the north (and from

Puntland to Somaliland) for export, the risk is considerable enough for importing countries to

suspect the presence of RVF in Somaliland and Puntland where animals are shipped and for

authorities of these States to carry out surveillance activities.

However, the application of statistically valid methods in Somalia is difficult due to the

pastoral nomadic context. The high mobility of livestock and the lack of a suitable sampling

frame for the lower administrative divisions make it nearly impossible to apply rigorous

random sampling methods.

Screening in Somaliland in 2001 and in Puntland in 2003 which targeted mainly sheep and

goats aged 1–2 years (97% of surveyed animals) revealed no signs compatible with the

disease but an overall sero-prevalence of 2 _ 0.02% (90/4570) and 5 _ 0.3% (206/4050),

respectively, Although results of the screening in Somaliland 2001 showed infection

prevalence in most region (five to six) the number of positives herds were concentrated in

Sanaag, Togdheer, and Sool region located within the Nugal Valley with a herd of prevalence

of 21 to 22 and (30%), this compared to 9 and 12% in Hargeisa and Sahil Regions.

this survey (GIS) software (Arcview1) was used to generate at random the required number

of sites within the area where sampling needs to take place, be it at zone, country, region or

even district level.As result of limited studies of rift valley fever in Somaliland this study was

aimed to show risk areas in Somaliland by using Arc GIS software version 9.3.1.

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LITERATURE REVIEW

1.2.1 Definition of the disease

Rift Valley fever (RVF) is acute or per acute disease of domestic ruminants in Africa and

Madagascar, caused by a mosquito- borne virus and characterized by fever, abortion, necrotic

hepatitis and haemorrhages, high mortality in young animals but infection are frequently in

apparent or mild,

1.2.2 Aetiology of RVF

RVFV has morphological and physiological properties typically of a member of the

phlebovirus of the Family Bunyaviriadae (Woods 2002).

A host cell derived bi-lipid- layer enveloped through which virus coded glycoprotein

composed of the three RNA segments, L(large),M(medium ),S(small )it contained in a

separate nucleocapsid within the viron , R FV is an enveloped virus with a diameter of 80 to

120 mm.

RVFV, which attaches to receptors on susceptible cells, it internalised by endocytosis and

replication occur in the cytoplasm by budding through endoplasmic reticulum in the Golgi

region (Struthers, & swanepoel 1982).

The virus can be grown in and readily produce cytopathic effect and plaque in virtually all

common continuous line and primary, including Primary calf and lamb kidney or tests cells,

the only exception s being primary macrophages and lymphoblastoid cell lines (Peter, 1981).

1.2.3 Epidemiology of the RVF

RVF is widespread in African and serious outbreaks have been encountered in both animals

and man in Egypt, Sudan, Kenya, South Africa, Zimbabwe, Zambia, and Senegal (Peters,

1981).

Over the last 40 years, numerous RVF outbreaks have occurred in most countries of sub-

Saharan Africa as well as Madagascar and Egypt (Meegan 1981, Zeller et al. 1997, House et

al. 1992).

Many of these outbreaks have been devastating to farming economies due to the associated

livestock losses and prohibited trade. In September 2000, RVF cases were confirmed in Saudi

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Arabia and Yemen, marking the first reported occurrence of the disease outside the African

continent.

This outbreak raised concerns that RVF virus may continue to spread to areas with a variety

of ecological conditions that were previously uninfected with the virus (Jupp et al. 2002,

Anyamba et al. 2006, Bird et al. 2007, Evans et al. 2007, WHO 2007b).

1.2.4 Pathogenesis of the RVF

After injection of the virus in tissue, initial replication occur at the site of infection followed

by viraemia and localisation of the virus in the target organs especially the liver, spleen and

kidneys. Further, replication of the virus in these organs amplifies the viraemia, severe

destruction of the hepatic cells, which is caused by the cytopathic effects for the virus (Peter,

1981).

Damage to the blood vessel walls causes vasculitis and widespread haemorrhages in the

affected tissue (Maar & Genfand 1979).

1.2.5 Implication of human healthy

human become infected from contact with infected tissue or from mosquito bite , in contrast

to the main vectors in the Egypt epidemic of 1977- 78 in south Africa people become infected

in contract with animals tissue , for instance where no such history can be obtained an it must

assumed that infection has resulted from mosquito bite.(Chambers, and warepoel. 1980)

Generally, person s who become affected are involve in livestock industry such farmers, who

assist in dystocia of livestock , farm labourers, who salvage carcasses for human consumption

,veterinarian and their assistants, and abattoir workers .( Maar & Genfand 1979)

Many reports of human becoming infected with RVF while, investigating the disease in the

field or laboratory. (Findlay, 1932)

Moreover, highest infection rates were found in workers in the by-product section of abattoir

in Zimbabwe Human infection results from infected virus with abraded skin, wound or mucus

membrane in the field during Egypt epidemic. (Brown 1981)The first known human fatality

was recorded in 1943 in laboratory worker in the USA soon after the initial isolation of the

virus (Schweitzer and Rivers, 1934), since the infection was complicated by thrombophlebitis

and patient died from pulmonary embolism.9

1.2.6 Geographic Distributions

Since the first major outbreak of RVF was recorded close to Lake Naivasha in Kenya in

1930-1931 (Daubney et al. 1931, CDC 2004b), RVF outbreaks in Africa have occurred as far

north as Egypt, throughout most of sub-Saharan Africa and as far south as Southern Africa

(House et al. 1992, Davies and Martin 2003). One of the most notable epizootics of RVF

occurred in Kenya in 1950-1951 and resulted in the death of an estimated 100,000 sheep

(CDC 2004b). The 1977 RVF outbreak in Egypt resulted in both animal and human cases

and it was believed to have started due to the importation of RVF virus infected domestic

animals from Sudan (Gad et al. 1986, Peters and Linthicum 1994). In 1987 transmission of

the RVF virus to humans in West Africa (Senegal, Mauritania) was linked to the altered

interactions between humans and mosquitoes that resulted from flooding of the lower Senegal

River during construction of the Senegal River dam project (CDC 2004b).

In 1997- 1998 a RVF outbreak in East Africa affected 89,000 people and caused over 400

deaths (Gerdes 2004). A severe form of the disease was seen in Mauritania (1998) where

many thousands of people became sick, 200 people died, and abortion losses in livestock

were heavy (CDC 2004b, Gerdes 2004).

The 2000 outbreak in Saudi Arabia and Yemen was particularly alarming as this was the first

time RVF virus was detected outside the African and created mosquito-breeding habitats. In

just four months, 155 people had died, and the outbreak had forced the closure of livestock

markets in Kenya devastating the economy of the region (CDC 2007).

From November 2006 through March 2007 RVF outbreaks occurred in Somalia, Tanzania,

Sudan, and Kenya (ProMed Mail 2007). In Kenya alone, there were 684 human cases with

155 deaths (Linthicum et al. 2008).

The most recent cases of clinical disease or infection (without clinical disease) involving

domestic ruminant livestock and humans have occurred in Madagascar, South Africa, and

Sudan (WHO 2008, OIE 2008, Kasari et al. 200

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1.2.7 Environmental Conditions

The role of environmental elements in the epidemiology of vector-borne diseases such as

RVF is well known. Environmental elements such as climate (e.g., temperature, humidity,

annual rainfall, intensity of rainfall), hydrology (e.g., proximity to lake/dam, irrigation,

accumulated water, proximity to river), and topography (e.g., elevation, land- cover)

influence vectorial capacity (House et al. 1992, Chevalier et al. 2004a, Turell et al. 2005,

Clements et al. 2006). To have high vectorial capacity, which in turn increases the

probability of contact between hosts and vectors and the likeliness of RVF virus

establishment and spread, competent vectors must be in an environment suitable for vector

bioecology (e.g., population dynamics and biting activity ) and virus transmission (Turell et

al. 2005).

Environmental conditions can affect the ability of mosquitoes to transmit arboviruses such as

RVF virus. For instance, the extrinsic incubation (EI) period (the time interval between

ingestion of the virus and subsequent transmission by the mosquito) of RVF virus depends on

ambient temperature (Brubaker and Turell 1998, Turell et al. 1985, Turell 1989, House et al.

1992, Diallo et al. 2005). In general, studies have consistently shown that the EI period is

inversely related to temperature (Turell et al. 1985). However, the magnitude of the effect of

temperature on both infection and transmission rates appears to vary for different virus-

mosquito combinations (Turell et al. 1s985).

Changes in climate (e.g., humidity, rainfall, and temperature) can alter the geographic ranges

and life cycles of plants, animals, insects, bacteria, and viruses (Longstreth and Wiseman

1989).

Climate changes conducive to vector bioecology in habitats frequented by host species could

result in vector population growth and increased disease transmission (Longstreth and

Wiseman 1989).

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1.2.8 Modes of Transmission

The mode of RVF virus transmission may be vector-borne, airborne or from direct contact

with body fluids of infected animals. May transmit the RVF virus mechanically (Hoch et al.

1985, House et al. 1992, Davies and Martin 2003), mosquitoes are the main RVF vectors

transmitting the virus to animals and humans (Meegan and Bailey 1988).

Many mosquitoes (e.g., Aedes, Anopheles, Culex, Eretmapodites, and Mansonia), transmit

the RVF virus and are infected naturally (Turell and Bailey 1987, Turell et al. 1990, Traore-

Lamizana et al. 2001, Chevalier et al. 2004a).

RVF virus is most often transmitted to humans by Aedes and Culex species of mosquitoes

(Linthicum et al. 1999, CDC 2004b).

Transmission of RVF virus to people working with livestock (e.g., when slaughtering or

handling infected animals or touching contaminated meat during the preparation of food or in

laboratory facilities) has frequently been an indicator of epizootic RVF virus activity (Davies

and Martin 2003). Infection through aerosol transmission of RVF virus has resulted from

contact with laboratory specimens containing the virus (Davies and Martin 2003, CDC

2004b), however, there have been no recorded direct human-to-human transmission of RVF

virus to date (Kasari et al. 2008).

RVF virus is maintained in the eggs of female floodwater Aedes mosquitoes, which breed in

isolated grassland depressions called dambos (Linthicum et al. 1985). The eggs are capable

of surviving in dry soil until the next heavy rainfall floods the dambos producing favourable

conditions for the eggs to hatch. Subsequently, very large numbers of adult mosquitoes

emerge (Linthicum et al. 1984; Davies et al. 1985, Ba et al. 2005, Anyamba et al. 2006) and,

if infected, transfer the RVF virus to livestock and other animals on which they feed. These

vertebrate blood meal hosts may become infected and develop a viremia (Linthicum et al.

1985, Evans et al. 2007). RVF epizootic periods result when waters persist a month or more

past the emergence of Aedes mosquitoes.

Secondary vector species (e.g., Culex spp.) to breed, generate large populations, feed on

animals with high levels of viremia (Linthicum et al. 1985, Davis and Martin 2003, Chevalier

et al. 2004a, Evans et al. 2007), and subsequently spread infection to animals beyond the area

of the original outbreaks (Linthicum et al. 1999, Anyamba et al. 2001, Woods 2002, CDC

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2004b). Cattle and sheep are the primary amplifiers of the disease (Meegan and Bailey 1988,

Longstreth and Wiseman 1989, Kasari et al. 2008). It has also been suggested that reservoir

animals (RVF infected rodents or wild ruminants) may be affecting domestic animals in

shared grasslands, and thus, maintain the virus during inter-epizootic periods. Sylvatic

(wildlife-mosquito) cycling of RVF virus could maintain the virus at low levels and enable

transmission of the virus from wildlife to wildlife and occasionally to livestock (Evans et al.

2007). Although Evans et al. 2007 found that African wild ruminants do become infected

with RVF virus,

Figure1, Rift valley fever virus transmission cycle (from Davies and Martin 2003).

1.2.9 Clinical sign of RVF

RVF virus is a zoonotic pathogen endemic to Africa (Peters and Linthicum 1994).

The susceptibility to and severity of RVF virus infection in numerous vertebrates (e.g., cattle,

sheep, goats, camels, rodents, wild ruminants, buffaloes, and antelopes, ) has been

determined during epizootics and in laboratory studies. Although RVF virus infects a wide

range of hosts, including humans, the most significant infections occur in domestic livestock

(e.g., sheep, cattle, goats, camels, and buffalo)

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1.2.9.1 Sheep and Cattle

The most important animal species in RVF epidemics are sheep and cattle. Both sheep and

cattle suffer significant mortality (e.g., greater than 90% in lambs and calves less than one

week of age) and abortion (virtually 100%) after infection, and they become sufficiently

viremic to infect many arthropod vector species (Peters and Linthicum 1994, House et al.

1992, EFSA 2005).

Sheep are extremely susceptible to RVF virus.

Onset is marked by high fever (40-42oC). Significant clinical features in affected lambs, kids,

and adult sheep also include listlessness, weakness, anorexia, rapid respiration, excessive

salivation, vomiting, fetid diarrhoea, and abortion (Daubney et al. 1931, House et al. 1992).

In older lambs and adults, the incubation period is between 24 and 72 hours, and the mortality

rate is 20-30% (House et al. 1992). The most severe reactions occur in newborn lambs and

kids, which die within hours of infection, rarely surviving more than 36 hours (Linthicum et

al. 2008).

Cattle Adult cattle exhibit clinical signs of disease infrequently, but some may develop acute

disease with clinical features similar to those of sheep. Frequently abortion is the only

manifestation in this species. The mortality rate in native adult non-pregnant cattle does not

usually exceed 10 percent (House et al. 1992). are less severely affected with RVF than

sheep.

The mortality rates in calves are generally lower than in lambs and vary widely (20-70%)

between outbreaks (Peters and Linthicum 1994, House et al. 1992, OIE 2008).

1.2.9.2 Goats

Goats are generally less severely affected than sheep (e.g., 1977-78 Egyptian outbreaks),

with much lower morbidity and mortality, fewer abortions, and less severe clinical signs

(Imam et al. 1979, Davies and Martin 2003). Abortion in goats and mortality in kids were

recorded in Kenya in 1930, the Sudan in 1973, South Africa and Namibia in 1974-75, and in

West Africa in 1987 (EFSA 2005). Older kids and goats may develop in apparent, per acute

or acute disease (OIE 2008).

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1.2.9.3 Camels

Camels do not normally show any clinical signs of RVF infection, however, antibodies to

RVFV have been detected in camels and RVF virus has been isolated from then during

epidemics, As in cattle and sheep, high abortion rate (100%) is a common consequence of the

infection in pregnant animals and neonatal mortality may occur in camel foals born during

RVF epizootic periods (Davies and Martin 2003)

in Senegal and South Africa (Gora et al. 2000, Chevalier et al. 2004a). Nevertheless, several

studies have suggested that rodents play no role in natural outbreaks of RVF in Africa

(Davies 1975, Swanepoel et al. 1978, EFSA 2005).

In addition, Poultry and wild birds are not susceptible to RVF virus (Davies and Martin

2003).

1.2.9.4 Humans

Humans with RVF typically have either no symptoms or mild Influenza-like illness with

fever, generalized weakness, muscle and joint pain, dizziness, photophobia, anorexia, and

sometimes nausea and vomiting (Davis and Martin 2003, CDC 2004b). Recovery usually

occurs within 4-7 days, however, in some cases the disease progresses to ocular disease.

Other, often fatal, complications include hemorrhagic fever and encephalitis (which can lead

to headaches, coma, or seizures). In humans the case mortality rate is generally low

(approximately 1%), but full recovery may be protracted and long-term ocular and

neurological complications have been reported (FAO 2008). However, in some cases

mortality can be as high as approximately 25% when proper public health interventions are

not undertaken during an epidemic/epizootic as was the case in Sudan in 2007 (WHO 2007b).

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1.2.10 Pathology of Rift Valley Fever

The hepatic lesions of RVF are essentially similar in all domestic animals and humans,

varying with the age of the affected individual. (Coetzer. 1977) In most severe lesions occur

in aborted sheep foetuses and new born- lambs in which the liver is usually moderately to

greatly enlarged , soft, friable and yellowish-born to dark reddish –brown in colour with

irregular congested patches and some lines haemorrhages of varying size scattered

throughout the parenchyma (Easterday,B.C.,1963)

Hepatic lesions in new- born lambs are almost invariably accompanied by numerous

petechiae and ecchymoses in the mucosa of the abomasums and its content are dark chocolate

–brown as result of the presence of partially digested blood.

Most mature sheep and cattle the spleen is slightly to moderately enlarged, with

haemorrhages in the capsule. Sometimes in Adult sheep edges of the spleen becomes dark-

blue-ish –red, circumscribed areas, 10 to 20 mm in diameter. (Coetzer, J.A.W and Mesi, G.d.

1975)

Lesions in newborn lambs are pyknosis and karyorrhexis of lypmnodes in lymphoid tissue,

cloudy swelling and hypotropic degeneration of the epithelial cells of the convoluted tubules

of the kidney and necrosis of the some cellular element in the glomeruli in ten per cent of

lambs, multifocal necrosis and haemorrhages in the adrenal cortex (Coetzer 1977).

Many animals have lung congestion, alveolar and interstitial oedema, haemorrhages, a few

fibrin thrombi in alveolar walls, emphysema, scattered neurophils infiltration and necrosis of

interlobular septa and peri-bronchial lymphoid tissue. (In human encephalitis is characterized

by focal necrosis with leukocyte infiltration and perivascular cuffing)(Van ders.1985).

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1.2.11 Diagnosis and Vaccination

The mild influenza-like symptoms in single human cases of RVF can be confused with many

viral diseases. However, a RVF epizootic outbreak should be suspected if there is a sudden

and widespread onset of many abortions in domestic animals, high neonatal mortality and

acute febrile disease with the presence of liver lesions. Cases of disease in people associated

with the affected animals also assist in making a tentative RVF diagnosis. Climatic and

ecological factors such as the presence of high mosquito populations and/or flooding of

grassland depressions can contribute to provisional RVF diagnoses (Davies and Martin

2003).

There are two types of laboratory tests used to confirm provisional RVF diagnoses. The first

is to identify or isolate the RVF virus or antigen. For example, the virus can be isolated via

intraperitoneal inoculated mice or hamsters, immunofluorescent or peroxidase staining of

tissue culture, simple agar gel immune diffusion tests using liver or spleen tissue, and

immune sera RT-PCR (reverse transcription-polymerase chain reaction) (Davies and Martin

2003, OIE 2008).

The second method to confirm provisional RVF diagnoses is to detect specific antibody to the

RVF virus. The presence of RVF specific antibody or IgM can be demonstrated with

enzyme-linked-immunosorbent serologic assay (ELISA), microtiter virus-serum

neutralization tests in tissue culture, or plaque reduction tests in tissue culture (Davies and

Martin 2003, OIE 2008).

No specific treatment exists for Rift Valley fever, In most humans RVF cases, symptoms are

mild and are managed with supportive therapy. Both inactivated and live-attenuated vaccines

have been developed to help control RVF outbreaks (House et al. 1992). Routine vaccination

of non-pregnant livestock in Africa is recommended prior to outbreaks, but has been

prohibitively expensive, leading to endemicity of RVF in most African countries (Balkhy et

al. 2003, Davies and Martin 2003, OIE 2008). No vaccine is currently licensed or

commercially available for humans or livestock in the United States (WHO 2007b, Britch et

al. 2007).

17

1.2.12 Control

Control of vectors and host movements is necessary to interrupt the epidemiological cycle of

RVF virus and thereby lessen the potential impact of an outbreak by lowering disease

transmission rates. Effective vector control methods include hormonal inhibitors such as

methoprene, widespread use of vehicle or aerial mounted insecticide sprays targeting adult

mosquito species, and strategic treatment of mosquito breeding habitats and soils with

larvicides and insecticides, respectively (Davies and Martin 2003).

Since viremic host animals could arrive in an uninfected country within the incubation

period, movement of animals for trade from enzootic/epizootic areas should be banned during

RVF epizootic periods (Davies and Martin 2003). Also important in controlling disease

spread to and among humans is public education to discourage practices that promote

transmission. This includes educating the public to avoid direct contact with the blood and

body fluids of sick or dead animals unless appropriate levels of personal protection are used

and to use personal protection against mosquito bites (e.g., long-sleeved shirts and pants and

mosquito repellent).

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1.2.13 Mapping of the RVF

A GIS is a computer-based system that combines digital geo-referenced (spatially- related)

and descriptive data for mapping and analysis (Brooker et al. 2002, Connor et al. 1995). One

of the main strengths of a GIS is its ability to integrate different types of spatial and non-

spatial data (Brooker et al. 2002).some examples of the types of data overlaid and analyzed

using GIS are population data (e.g., census, socio-economic, and animal population data),

land-use and public infrastructure data, transportation networks data (e.g., roads and

railways), health infrastructure and epidemiological data (e.g., data on mortality, morbidity,

disease distribution and healthcare facilities), and environmental and ecological data

(e.g.,climate and vegetation data) (Kamel et al. 2001).

GIS technology can be used to manage and monitor different aspects of disease, from

incident tracking to epidemiologic analysis and assessment of risks (Allen and Wong 2006).

For example, a GIS can be used to map available epidemiological information and relate it to

factors known to influence the distribution of infectious diseases, such as climate and other

environmental factors that affect vector bioecology (Brooker et al. 2002, Allen and Wong

2006).

1.3 GENERALAND SPECIFIC OBJECTIVES

1.3.1 GENERAL OBJECTIVES

The general objectives of this mini thesis are to show areas of risk of rift valley fever in

Somaliland regions.

1.3.2 SPECIFIC OBJECTIVES

To indicate high-risk areas in Somaliland regions by using ArcGIS software

To estimate prevalence of surveyed four regions in Somaliland.

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CHAPTER TWO MATERIALS AND METHODS

2.1 Data Collection

The input of data was obtained from SAHSP office in Hargeisa, where relevant information

was expected to be available like Ministry of livestock. In addition, data were selected in

survey of four regions in Somaliland where ArcGIS software /Stata IC 11.0 was used.

2.2 Data Management and Analysis

Data from SAHSP were managed and entered into databases by using ArcGIS version 9.13

(Brooker) 2002, (Connor et al. 1995) due to short time of study. For the statistical analysis

the software Stata IC/11 was used to carry out exploratory analysis of potential RVF Also

were used data input of excel Microsoft programme.

2.3 Administrative structure of Somaliland

The Somaliland administrative structure has frequently been subject to Modification, to this serological study of mapping RVF there are 4 regions composed of (12) districts. Each region composed 30 locations and out of this four regions were selected where 900 samples were extracted and the animals bleed were Sheep and Goat in those four regions. But Age group were different according sheep and goat.

Table 1: Structure of the different administrative levels of sampling

Included in the above administrative level

RegionDistrict Location Sites

Total 4 12 30 900

Mode - 164 30 313

Average 225 75 30 331

Range 198 134 5 38

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Table 2: List of relevant variables included in the database along with the number of observations available

Variable Number of samples for which it was recorded

% of samples for which it was recorded

Localization

Region900 100%

District900 100%

Location900 100%

Site900 100%

Species

Goat456 51%

Sheep444 49%

Age1-5

Sex

Male356 40%

Female544 60%

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Map2. Shows sampling location

2.4 Laboratory techniques

Field collection samples during the survey of serological investigation samples were sent to

Nairobi laboratory were used IgG antibodies of ELISA to confirm the presence of RVF Virus

surveyed regions in Somaliland.

2.5 Description of the Study area

The republic of Somaliland is located in the Horn of Africa. Its boundaries are defined by the

Gulf of Aden to the north, Somalia in the east, Ethiopia in the South West, and in the

northwest. It lies between the 08°00' – 11°30' parallel north of the equator and between

42°30' – 49°00' meridian east of Greenwich. The capital of Republic of Somaliland is the city

of Hargeisa (elevation 1347 meters) but the country has a total area of 137,600 km2 with

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coastline that extends about 850km along the southern African shores of the Gulf of Aden

however, The population of the Somaliland is about 3.5 million,

The country is divided into six regions namely; Maroodi jex, Awdal, Sahil, Togdheer, Sool

and Sanaag that are sub divided into 33 districts.

Figure2 shows map of study area

2.5.1 Climate and Geography

Somaliland is situating between 8o and 12o north of the equator. Climatically the country has

semi arid warm weather, where the daily average temperature ranges from 25o to 35Co.

The country’s three distinguish topographical features are the GUBAN, or the hot arid coastal

plains; the rolling highland of the Oogo which also contains some rugged and inaccessible

mountain ranges and Hawd plateau which stretches well into Ethiopian territory Southwards.

The coastal plain Oogo is very hot, with maximum temperature balanced around 30 oC

throughout the year, reaching 40oC-45oC between May and September. Rainfall is generally

scarce, and vegetation is sparse. Somaliland is characterized by its great variations in

topography, climate and population. The four distinct seasons are: two main rainy seasons 23

known as “GU “or spring from April to June and short season “Deyr”or autumn rainy period

from September to November and two dry seasons of” Hagaa” or summer form July to

August and then long dry, cold “Jilaal”or winter from December to March.

CHAPTER THREE RESULT

Table 1: Prevalence of Rift Valley in the four surveyed regions

Regions

Number of samples collected in each region and % of the wholesurvey

Prevalence with 95% Confidence Intervals

Marodi jex 60 (7%) 0.15 (0.05-0.25)

Sanaag 318 (35%) 0.116352201 (0.11-0.15)

Sool 270 (30%) 0.185185 (0.18-0.25)

Togdheer 252 (28%) 0.107142827 (0.10-0.14)

Total 900 (100%) 0.137 (0.13-0.15)

Map1 of Rift Valley Survey Result

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Map2 shows Rift Valley Risk sites serological status

Map3 shows Somaliland Digital Elevation Model (DEM)

Map 4 shows Somaliland Rift Valley Risk Areas

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CHAPER FOUR DISCUSSION

4.1 Discussion

As one way of extracting information, desk review has been used due to the short time frame

of the study period. Therefore, an already stored data has been received from SAHSP

regional office through Dr. Ismail Kane with permission from Ministry of livestock. And the

data was analyzed in ArcGIS view programme to identify the high risk areas for rift valley

fever in Somaliland regions.

As recommended by James (1998) and applied by Terra Nuova in a previous surveys in

Somaliland and Puntland, and to overcome the lack of sampling frame due to high mobility

of animals which encompasses as one of the pastoral nature of the communities surveyed,

GIS system has been sorted out as the only method to help us achieve our objective to I

identify the high risk areas in Somaliland.

Over all sero-prevalence of this study was (14%) which is high according to previous reports

in Somaliland (Berkvens 2001) and in punt-land 2003 has prevalence of (5%) because in

2001 rainfall was not so much compared to 2002 – 2004 that is why carrier vectors highly

spread of RVF virus in those animals which are susceptible to the disease.

However, the comparison made between four surveyed regions risk areas of rift valley fever

in Somaliland are Sool and Marodi jex as show on Map 5 compared to Sanaag and Togdheer

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and this is in agreement with previous studies conducted by Terra Nuova with help of

Ministry of livestock. (Berkvnes 2001).

In general as table1 in results shows comparison made on prevalence of RVF in four

surveyed regions in Somaliland with their interval confidence respectively 95%, Sool has

19%, (0.18-0.25) Marodi jex15% (0.05-0.25) Sanaag 12% (0.11-0.15),Togdheer

0.11.%(0.10-0.14),

As result of prevalence Sool and Marodi jex has the highest prevalence of the disease and this

might be the movement of animals in Sool to Nugal valley which provide a favourable

condition to vectors for the growth of the vector prevails and provide a favourable condition,

exposing the area to reveal high case of positive RVF rising to the top of risk areas identified

in the study. Thus, the root cause of detecting the disease in such arid areas can be the change

of movement pattern of animals observed in the areas.

Admittedly, the landscape of these region with positive case can be allowing the disease to

get established as in shown in Map 3 in the result this study and these regions borders like

Ethiopia and surrounding districts have a large water catchment surface and at the same time

borders.

Sool located to Nugal which have a very large valley that often harbours the most favourable

condition for the survival and proliferation of Aedes spp (low elevation ground, high

temperature, superficial and underground rivers which supply sporadic natural pools

surrounded by dense vegetations) it found Grazing areas and watering points and the Sool

pastoral community moves towards the valley in search of water and pasture and this

movement is facilitated by the blood relation to the inhabitants in the valley while Marodi jex

pastoral communities moves towards Ethiopia also Marodi jex risk factor are plat and

watering point that is why become high at risk of disease also those districts have water

catchments and watering points that cause vector to be abundant.

Usually, the disease is basically dependent on the weather pattern in the study area as it is

vector. And in general Somaliland is termed to be laid in the Arid of east Africa giving that

RVF is very hard to get established in the area as endemic disease. After, 2000 embargo by

the Arab governments there launched a joint rift valley survey by Terra Nuova and Ministry

of livestock revealing that there was a recent out breaks or high viral circulation in Sanaag

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and Sool which the recent outbreak idea was refuted as it did not happen before the study

however, the expectation of RVF outbreak was high.

As shows table 2 that sheep 49% are the least reared species when compared to goats 51%

while the herd is dominated by the female (60%) of herds and this is because, apart from

breeding, males (40%) are sold as source of cash for the household to cater other domestic

needs like sugar, drugs, food and clothes.

CHAPTER FOUR CONCLUSIONS AND RECOMMENDATION

5.1 Conclusion

This study was aimed at producing by mapping RVF of risk areas in Somaliland regions, so

that it can help to improve the management and control of RVF vector in those regions,

although the environment drivers that determine the life cycle of the vector with high risks

like Sool and Maroodi jex compared to Sanaag and Togdheer, the most importance to

identify and visualize areas of high rift valley fever in Somaliland is to put place areas which

are likely to become infected through sero- monitoring of those areas.

The sampling method using a GIS facilitated significantly the implementation of the RFV

investigation in Somaliland. in particular, high-risk areas of four regions in Somaliland. They

can be monitored and analysed newly available technologies of ArcGIS soft ware.

Similarly, a survey was carried out in Somaliland of screening sampling by using ArcGIS

software in 2001.

This mini thesis is important to create operational maps that could help the vector control and

priority areas of risk for disease control in future.

Hence, the maps were constructed to allow targeting with regions of high risk areas of RVF,

accordingly.

5.1 Recommendation

Based on finding of this study of mapping risk areas four of Somaliland regions, following

recommendations were given as follows

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Ministry of livestock and relevant veterinary NGO’s should develop the capacity to

identify ecological factors of mosquitoes to insure risk areas or create buffer zone.

To make public awareness about controlling the vector and to avoid the spread of

disease in those regions.

Those regions were at risk for the establishment of RVF and should provide

insecticide in human also Spraying could help the people to recover because the

disease can be transmitting through contact of tissue of the infected animals and

through mosquito bite from affected person to another person.

Community to use proper dispose of trash or anything that hold water.

ANNEX ONE

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