EMERGING & RE-EMERGING [parasitic] INFECTIONSINIMMUNOCOMPETENT & IMMUNOCOMPROMISED HOSTS
Rumala MorelDepartment of Parasitology
Faculty of MedicinePeradeniya
Year 3 2005/06 Batch
• Mad cow disease• H5N1 avian influenza• Severe Acute Respiratory Syndrome
(SARS) • Ebola virus• Hantavirus• Monkeypox• Swine flu
New Diseases EmergeOld Diseases Re-emerge
Objectives
• Define emerging & re-emerging infections• List the emerging & re-emerging parasitic
infections which are important globally & in SL• Briefly describe the factors which predispose to
emergence & re-emergence of infections in immunocompetent & immunocompromised hosts
• Recognize the current handicaps when dealing with the risks of these infections
• Briefly describe the preventive aspects of these infections
"emerging," "re-emerging," or "endemic"
Re-emerging = diseases that once were major
health problems globally or in a particular country, and then declined dramatically, but are again becoming health problems for a significant proportion of the population.
• Diseases thought to be adequately controlled making a “comeback” are “re-emerging”
Emerging = diseases that have not occurredin humans before orthat occurred onlyin small numbersin isolated places.
"endemic" a long term problem.Never significantly decliningEg. pneumonia
• Emerging diseases = new infections that arise from changes in existing organisms
or • known infections that spread to new geographic
areas or populations• Incidence of such a disease in people increases
over 20 years or threatens to increase
New Diseases Emerge
WHAT ARE EMERGING DISEASE ‘HOT SPOTS’?Regions where new emerging infectious diseases
are most likely to originate. Usually tropical – developing countries ill equipped to cope
Old Diseases Re-Emerge(A) EVOLUTION OF THE INFECTIOUS AGENT• Mutations in bacterial genes that confer
resistance to antibiotics – 20% • Multidrug-resistant & extremely drug-resistant TB • Multi drug resistant P.falciparum
(B) REDUCED HUMAN IMMUNITY• Immunization failure
(breakdowns in public health measures)a greater proportion of susceptible individuals in a population and an increased reservoir of the infectious agent.
• Increased number of immunocompromised hosts - due to the stress of famine, war,
or disease
ZOONOSES In most cases (60%) that’s an infection that’s already out there in nature – may be a virus that’s naturally infecting some other species.
Ecological changes - puts humans in contact with the virus. Usually due to human activities
WHY EMERGE? FACTORS PREDISPOSING TO EMERGENCE
1st step Introduction of an infection for the first time into the
human population
WHY EMERGE? FACTORS PREDISPOSING TO EMERGENCE
• ENVIRONMENTAL CHANGE tropical forests are cleared to make way for new roads, displacing disease-carrying animals and insects and increased human traffic through previously isolated areas
• URBANIZATION - person-to-person transmission • POOR PRIMARY HEALTH CARE
public health services may not be equipped to deal with some infectious outbreaks
Globally important Emerging & Re-emerging Infectious Diseases
RE-EMERGINGtuberculosismalariaschistosomiasis
EMERGINGAIDS cholera CJDEbola hemorrhagic
feverinfluenzaLegionnaire disease Lyme disease
List of NIAID* Emerging and Re-emerging Diseases
– Group I—Pathogens Newly Recognized in the Past Two Decades
– Group II—Re-emerging Pathogens– Group III—Agents with Bioterrorism Potential
• NIAID—Category A • NIAID—Category B • NIAID—Category C
* NIAID = National Institute of Allergy & Infectious Diseases - USA
NIAID Group 3 -Category B
Food & Waterborne pathogens
Cryptosporidium parvum
Cyclospora cayatanensis
Giardia lamblia Entamoeba
histolytica Toxoplasma gondii
Emerging and Re-emerging Parasites
NIAID Group 1 - Pathogens newly recognized in past two decadesAcanthamoebaMicrosporidia
Encephalitozoon cuniculiEncephalitozoon hellemEnterocytozoon bieneusi
Encephalitozoon cuniculi
extruded polar filament.
coiled polar filament, thin wall with endospore,and exospore
What is a Pandemic?
• "The world is now at the start of the 2009 influenza pandemic 30,000 confirmed cases from 74 countries” 11th June 2009
• WHO increases pandemic alert level to phase 6 "community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5.
• " Phase 5 is characterized by human-to-human transmission of the virus into at least 2 countries in 1 WHO region.
• H1N1 immunization campaign
????Panic & Epidemic???
pandemic is a global disease outbreak
Global Warming
• A temperature change of several degrees may make temperate zones more hospitable to vectors of tropical diseases
• Malaria, Dengue - mosquitoes• Schistosomiasis – snails
• At the same time, tropical areas may become less hospitable to some of the same diseases.
Schistosomiasis
? Spreading fromTROPICAL toTEMPERATE regionsDue to spread of snail vectorWith GLOBAL WARMING
crayfish as a biocontrol agent for the snail vector of human schistosomiasis, a disease that has resurfaced as a growing problem due to China's rapid land-use change.
Transmission of pathogens with reduced
dependence on host mobility
• water-borne –diarrhoeal agents• attendant-borne [eg. Escherichia coli]
Emerging hospital-acquired pathogens• Humans create pathways for transmission
eg. spreading HIV through needle sharing, blood transfusion, commercial sex trade. It is now pandemic in spite of its relatively inefficient transmission.
• mosquito-transmitted diseases: water is the limiting step. So irrigation projects, building of dams, cause an increasein the mosquito population, and suddenly you see anincrease in the diseases
MALARIA• WHO Global Malaria
Programme aims not only to reducethe burden of
malaria in endemic areas,
but also to Limit the
geographical extent of malaria in the world.
Local Elimination the complete interruptionof mosquito-borne malaria transmission in adefined geographical area
Key interventions to control malaria include:• prompt and effective
treatment with artemisinin-based combination therapies; • use of insecticidal nets by
people at risk; And• indoor residual spraying to control the vector mosquitoes.
Emerging Parasitic Diseases in Sri Lanka
• Leishmaniasis• Cryptosporidiosis• Dirofilariasis• Toxocariasis• Cutaneous Larva Migrans
Promastigotes Amastigotes
Sand fly
Cutaneous leishmaniasis is established
Visceral leishmaniasis is
Emerging in Sri Lanka
Cutaneous leishmaniasis in Sri Lanka
Quick Look at Current HIV Statistics in SL as of End March 2009
Quick Look at Current HIV Statistics in SL as of End March 2009
HIV IN SL – March 2009HIV : 1099AIDS : 293AIDS Deaths : 189
Children living with HIV : 37
Since 1981, HIV/AIDS has infected 60 million & killed half of them.2 million die every year & every 15 seconds a person is infected with HIV
“test and treat” strategy of universal, voluntary, annual HIV testing and immediate treatment for those who test positive.
High-risk populations In SL CSWs, Drug users, Internal migrantsand transport workers Global fund for AIDS/TB/Malaria ( GFATM)
Community-based outreachstrategies and new social-mediatools like mobile phones,the Internet, Twitter, and Facebook
Control of HIV/AIDS
Guidelines for Preventing Opportunistic Infections Among HIV-Infected Persons --- 2002
Recommendations of the U.S. Public Health Service and the Infectious Diseases Society of America*
(A) preventing first episodes of disease by chemoprophylaxis or vaccination (primary prophylaxis), and preventing disease recurrence (secondary prophylaxis).
(B) PREVENTING EXPOSURE TO PATHOGENS• oral-anal contact - to reduce the risk for intestinal
infections e.g., cryptosporidiosis, shigellosis, campylobacteriosis, amebiasis, giardiasis, and hepatitis
• contact with animals - cryptosporidiosis, toxoplasmosis, salmonellosis, campylobacteriosis, or Bartonella infection.
HIV infected - PREVENTING EXPOSURE TO PATHOGENS (contd)
• New pet – avoid animals aged <6 months or <1 year for cats –toxoplasmosis,cryptosporidiosis, Bartonella infection (avoid cat bite/scratches, flea control), salmonellosis, and campylobacteriosis
• Poultry and meat are safest when adequate cooking is confirmed with a thermometer (internal temperature of 180ºF for poultry and 165ºF for red meats). no trace of pink
• Uncooked meats should not be allowed to come in contact with other foods; hands, cutting boards, counters, and knives and other utensils should be washed thoroughly after contact with uncooked foods (BIII).
Cryptosporidium parvum: an emerging pathogen
six major outbreaks in the United States - contamination of drinking waterhighly environmentally resistant cyst of C. parvum survives drinking water filtrations chlorination
oocysts do not survive cooking
2 types of oocyststhick-walled - excreted thin-walled -autoinfection
Cryptosporidium
• Watery diarrhea (up to 20 liters/day)
• dehydration, weight loss, abdominal pain, fever, nausea and vomiting.
• In immunocompetent – self limited -1 to 2 wks
• immunocompromisedchronic and severe diarrhoeaDisseminated - lungs
feco-oralwater contaminated by livestock mammal feces HIGH RISK GROUPSinfants and younger children
in day-care centers -frequent diaper-changing
those whose drinking water is unfiltered and untreated
Farmers / veterinarians
TRANSMISSION CLINICAL FEATURES
50% infective dose (ID50) of C. parvum is only 132 oocysts for healthy persons
CRYPTOSPORDIOSIS
• Laboratory Diagnosis:Acid-fast staining
• immunofluorescence microscopy
method of choice - greatest sensitivity and specificity
• enzyme immunoassays• Molecular methods - research tool.
TREATMENT OF CRYPTOSPORIDIOSISParomomycin.
THE U.S. PUBLIC HEALTH SERVICEAND INFECTIONS DISEASES SOCIETY OF AMERICA
BOTH RECOMMEND THAT HIV-INFECTED INDIVIDUALSSHOULD NOT BRING INTO THEIR HOMES:
Animals with diarrheaStray dogs or cats
Dogs or cats under age 6 months
Cyclospora cayetanensis
Life Cycle
of
Cyclospora
cayetanensis
Acanthameoba spp.
In healthy -Acanthamoeba keratitis Immunosuppressed -
Granulomatous Amebic Encephalitis (GAE) Disseminated infection
Isolated from water, soil, air conditioning etc
Emerging & Re-emerging Infectious Diseases Surveillance & Control
• Disease surveillance is concentrated not in developing countries, where emerging diseases are most likely to arise, but in developed countries that can afford laboratories
• Global disease surveillance networks(1) U.S. Defense Department’s GEIS (2) WHO - Global Outbreak Alert and Response Network (GOARN)
• Identify, confirm and respond to outbreaks of international importance.
Emerging Pathogens Institute -prevent or contain new and re-emerging diseases
References
• “Global Trends in Emerging Infectious Diseases,” February 2008 in the journal Nature.
SGD questions
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