Florida Department of Agriculture and Consumer Florida Department of Agriculture and Consumer ServicesServices Charles H. Bronson, CommissionerCharles H. Bronson, Commissioner

Dr. Thomas J. Holt, State VeterinarianFDACS, Division of Animal Industry

October 4, 2008

Rift Valley Fever - A Florida Animal Health Perspective

Rift Valley Fever (RVF)

• Epidemic hepatitis of ruminants• High mortality in neonates and abortion• RNA virus vectored by mosquitoes• Zoonotic with acute influenza-like illness with

some blindness, encephalitis and death• Endemic to east Africa – Rift Valley region with

outbreaks in north Africa and Middle East• Viewed as significant threat to the United States

1. RVF Ecology/Epidemiology

• Disease caused by virus in Family Bunyaviridae, Genus Phebovirus

• First described in Kenya 1931 after epizootic in sheep on a farm north of Lake Naivasha

• Viral zoonosis that affects livestock and humans in Africa

– affects primarily domestic livestock – horses, pigs, poultry and wild birds non-

susceptible?• Human symptoms - a flu-like illness with fever,

weakness, back pain, dizziness, and weight loss – leading to hemorrhage (severe bleeding), encephalitis (inflammation of the brain), or severe eye complications

• Treatment – None, experimental use of antiviral ribavirin

• No U.S. licensed animal or human vaccine • Mortality – 1-25% in humans, 80-100% in livestock

Lake Naivasha,

Kenya

Clinical RVF in CattleFeature Characteristics

Incubation period 1-6 days

Clinical signs Calves:—Fever of 40°-42°C (104°-106°F)—Depression—Icterus—Anorexia and weakness—Listlessness—Evident abdominal pain

Adults:—Fever of 40°-42°C (104°-106°F)—Excessive salivation—Anorexia—Weakness—Near 100% abortion, fetid diarrhea—Fall in milk yield—Nasal discharge

Case-fatality rate —Calves: 10%-70%—Adults: <10% in indigenous breeds

Clinical features in Sheep and Goats

Feature Characteristics

Incubation period Lambs: 12-36 hrs.

Adults: 1-6 days

Clinical signs Lambs:—Fever of 40°-42°C (104°-107°F)—Anorexia and weakness—Listlessness—Evident abdominal pain

Adults:—Fever of 40°-41°C (104°-106°F)—Mucopurulent nasal discharge—Vomiting—Anorexia—Listlessness—Diarrhea—Icterus

Complications —Abortion rates can reach 100% (aborted fetus often autolysed)—Peracute hepatic disease in lambs and kids <1 wk. of age—Hepatitis—Cerebral infections—Ocular infections

Case-fatality rate Lambs—<1 wk. of age: as high as 100%—>1 wk. of age: as high as 20%Adults: 20%-30%

Short Duration Viremia Examples: RVF, CHIK, CCHF

Short Duration Viremia Examples: RVF, CHIK, CCHF

TimeTime3-5 3-5 daysdays

3-5 3-5 daysdays

Fever

Virus/Ag

Nt/ELISA Antibody

IgM Antibody

SummaryPatterns of RVF Infection

• Incubation period for RVF is relatively short (3-5 days in adult humans, 12 hours in young animals)

• Fever coincides with short viremia• Viremia 3-10 days in humans• Viremia 2-5 days in cattle• Amplitude of viremia high (>108 PFU/ml))• Long-lasting immune response• Lifelong IgG and neutralization antibodies in humans

RVF Transmission

Biological – Mosquitoes

Mechanical – Flies, midges, other arthropods

Aerosol – Direct contact with infected tissues

Aedes mcintoshi infected with RVF virus transovarially

Culex species - important secondary vectors of RVF

Possible Sources of Introduction

Infected Vectors

Viremic Animals

Viremic People

Contaminated Viscera and Tissues

Contaminated Raw Milk

Potential Impacts of a Zoonotic Disease Like RVF

• Direct and hidden costs• Costs due to potential loss• Effect on agricultural and public health industry• Effects on economy at large (livestock feed suppliers,

health care insurance, and food-service industry) • Loss of confidence in food source• BSE (1986) in UK cost EU > $100 billion• OIE imposes 4-year trade ban on country with RVF• OIE lifts ban after 6 months disease free• U.S. had $5.7 billion beef-related exports in 2003

Epidemiology Considerations in U.S.

• Zoonotic agent• Wide variety of mammals (deer, rodents,

birds?)• Mosquito species• Vertical transmission in mosquitoes • Few U.S. veterinarians have experience

with controlling vector-borne disease

Implications of RVF Outbreak For U.S. and other Countries• National – the U.S. is a major hub of global travel, a major hub of immigration

and commerce, large civilian and military presence all over the world and specifically Horn Africa – govt., military, business, aid – so the disease could impact U.S. national interests directly

• Importation/introduction of RVF in the U.S. directly– Risk not determined but even more serious than above– Decimation of the domestic beef cattle industry– No exports– Loss of confidence in the beef industry, also will happen with the sheep and goat

industries, affect dairy cattle because of safety concerns, abortions of pregnant animals and death in young animals

• Disease in people – – There is no U.S. approved animal or human vaccine – Only way to control it is through mosquito control – Rivabirin – anti-viral drug – interferes with the replication of the virus genome, can

reduce human severity of the disease but is in short supply and may not be used on a large scale

• Could be introduced into U.S. wildlife population – Deer population and other wild ungulates at high risk

• Could become endemic in deer population in some or all regions of U.S./North America• Could serve as a reservoir of the virus for humans and domestic animals

Implications of RVF Outbreak

For U.S. and other Countries (continued)• Could be introduced into U.S. mosquitoes

– Various Culex and some Aedes species of mosquitoes are susceptible to the virus and will transmit virus efficiently

– Transmission by mosquitoes would be widespread in all regions of continental U.S.

– Virus might become established transovarially in Aedes mosquito

• Virus transmitted to eggs of mosquito and then passed from larvae, pupae to adult

• Known to occur in Africa

• Virus would be virtually impossible to eradicate/eliminate

Potential Mechanisms of RVF Introduction into the U.S.

• International travel by people– Many people travel back and forth between U.S. and RVF endemic countries– Many FNs travel from endemic countries to the U.S.– Travelers/visitors on commercial flights from RVF endemic areas can reach virtually any U.S. city in 36 hrs. (shorter than the incubation period of RVF)– Immigrants - many people immigrate to the U.S. from RVF endemic areas– Returning U.S. military forces previously deployed in RVF endemic areas

• By mosquitoes – On an airplane where there is a direct flight between an endemic region and the

U.S. – not common, but can happen – also by military flights – Maritime containers/ships: Increased where you have plants-water with rodents

• may take weeks, but you have the life cycle going on, including virus transmission• there are maritime container ports near JKI - Kenya

– Example:

– Containers are sealed and may contain mosquitoes: » in a day or two, the container is put on a truck and driven to Mombasa » put on a ship » ship could go to multiple U.S. ports» e.g.. New Orleans, may be opened there or remain closed and be transported to

thousands of inland ports via truck rail or ship and open virtually at any city in the U.S.

Potential Mechanisms of RVF Introduction into the U.S. (cont.)

• Movement of infected animals into the U.S.

– Rare from Africa but could enter easily via Mexico

• Intentional introduction

– Somebody in EA knows an outbreak is going on

– Does not have to be sophisticated

– Could bring infected animal tissue

– If more sophisticated, could bring the virus in a container

– Infect domestic animal by inoculation

Rift Valley Fever Tabletop Exercise

hosted by the:

Florida Department of Agriculture and Consumer Services/Division of Animal Industry

prepared by the:

University of Florida/College of Veterinary Medicine

Dr. Paul Gibbs

November 18-20, 2008

State Emergency Operations Center (SEOC)

Exercise Purpose

• The purpose of this exercise will be to give participants an opportunity to plan, initiate, and evaluate current response concepts, and capabilities in a simulated introduction and outbreak of Rift Valley Fever in Florida

Exercise Focus

• This exercise will focus on multiagency coordination and the critical decisions of key state regulatory/emergency response agencies in the first days of the simulated disease outbreak

SEOC War Room

State Warning Point

Scheduled Participating Agencies

• Florida Division of Emergency Management

• Florida Department of Health

• Florida Fish and Wildlife Conservation Commission

• FDACS/Office of Agricultural Law Enforcement

• FDACS/Agricultural Environmental Services

• FDACS/Division of Animal Industry

• FDACS/Division of Dairy

• FDACS/Commissioner’s Office

• USDA/APHIS

University of Florida,College of Veterinary Medicine

The Florida Veterinary Corps (The Corps) has been established to enlist veterinarians and veterinary technicians who are willing to volunteer their services in responding to animal emergencies in the state of Florida.

Role of Private Veterinarians in Emergency Response

• Local Expert Consultations

• Disease Management for Specific Clients coordinated with ICS

• Serve as ICS Responder – Paid or Unpaid• Industry Outreach

• Planning/Operations