zoonoses 04apr2007

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Great presentation of zoonosis with appropriate examples.

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Zoonoses: an Epidemiologic Perspective: 

Zoonoses: an Epidemiologic Perspective Dr. Lynora Saxinger ‘ID’ ologist April 5, 2006


Objectives Review definition of zoonotic disease Using representative examples, discuss Factors affecting transmission Geographic/environmental influences Learn about the epidemiology of the following examples of zoonotic disease Echinococcosis Leptospirosis Brucellosis Lyme disease


Resources Chapter 314 – Mandell “Principles and Practice of Infectious Diseases” Disease specific chapters in Mandell Chapter 12 (Pg 301), Nelson text Emerging and New Infectious Diseases EMERGING INFECTIOUS DISEASES (Journal) http://www.cdc.gov/ncidod/eid/ Zoonotic Infections in Travellers to the Tropics Prim Care Clin Off Pract 29(4), Dec 2002 Strickland – Tropical Medicine, 8th Ed. Chapter 135 pg 979 “Zoonoses”


Definitions An epizootic an epidemic in a population of wild animals A vector is a living organism that carries a disease-causing organism to new hosts  A definitive host is the host in which parasites go through their sexual stage The intermediate host can harbor the parasite but it cannot undergo sexual reproduction The reservoir host is the host that a pathogen normally resides in


ZOONOSES: DEFINITION Complex group of diseases caused by diverse microorganisms that usually reside in / cause disease in ANIMALS Characteristics of these diseases: NONHUMAN VERTEBRATE RESERVOIR TRANSMISSION TO PEOPLE direct by airborne exposure, contact, ingestion of animal products (orthozoonoses) May require more than one vertebrate host (cyclozoonoses) invertebrate intermediate (metazoonoses) nonanimal sites and reservoirs and vertebrates in cycle (saprozoonoses) Cause a recognized CLINICAL SYNDROME infected persons develop disease


Zoonoses: > 200 zoonotic pathogens include the largest parasites (macrohelminths) to the smallest pathogens (prions, viruses) Prions (bovine spongioform encephalopathy) Viruses (Dengue, Hanta, West Nile, rabies) Bacteria (Brucellosis, Leptospirosis, Q fever, Plague) Protozoans (Babesiosis, Chagas disease) Helminths (trichinosis, echinococcosis) Worldwide importance historical (rabies, bubonic plague, typhus) contemporary (Lyme disease, BSE) Most important infections historically were acquired from animals, those that required a human reservoir only became possible only after populations reached a critical size

People, Animals, Bugs: 

People, Animals, Bugs

Zoonoses- Where, Why, How?: 

Zoonoses- Where, Why, How? Global distribution Exotic locales- adventure tourism Domestic and laboratory animal contacts Pets Have economic and political implications- e.g. emergence of BSE in UK, threatened emergence in Canada and implications for trade,

Factors Influencing the Epidemiology of Zoonoses: 

Factors Influencing the Epidemiology of Zoonoses Largely dependent on factors influencing animal and vector populations- intermediate hosts allow persistence even when human population is minimal Type and risk of human encounters with vector and reservoirs affects infection risk: finding “new” diseases Humans often dead end hosts- limited interspecies transmission and often limited infectivity among humans (except pneumonic plague, yellow fever)

Factors Influencing the Epidemiology of Zoonoses: 

Factors Influencing the Epidemiology of Zoonoses Geography and Human Activities LYME DISEASE – regrowth of forest in NE US with ↑deer and tick populations- recognized in 1970s, and reportable since 1991: 10-15 000 cases/year RABIES – Importation of infected raccoons to West Virginian hunting camps in 1978- started a rabies epizootic to Middle Atlantic, NE US states and Ontario (racoons, skunks, cats, rabbits…)

Rabies Cases: 

Rabies Cases 1969-99

Factors Influencing the Epidemiology of Zoonoses: 

Factors Influencing the Epidemiology of Zoonoses Travel- distribution of zoonotic diseases impact immunization choices, medications, food and drink advice… Military Actions – movement of large numbers of suceptible soldiers into endemic areas ↑ awareness of diseases Korean Hemorrhagic Fever (UN troops) Q fever after Desert Storm Cutaneous leishmaniasis- Sinai Desert Crimean War- First description brucellosis- Marston

Factors Influencing the Epidemiology of Zoonoses: 

Factors Influencing the Epidemiology of Zoonoses CLIMATE Temperature, soil, moisture conditions Temperature affects arthropod vectors, vegetation, and animal migration Anthrax spores: disease more likely if warm “incubator” soil conditions met Ticks transmitting Lyme and RMSF – not found in colder, Northern climate Leptospirosis and rain

Factors Influencing the Epidemiology of Zoonoses: 

Factors Influencing the Epidemiology of Zoonoses Animal, Avian, Aquatic HOSTS Host Susceptibility (genetic, natural and acquired immunity) influences spread Rabies vaccination of dogs in developed world has almost eliminated disease Domestic animals may acquire tularemia, plague, rabies, or carry infected ticks Migrating birds can carry arboviruses Aquatic mammals can act as sources for Giardia lamblia (waterborne) or tularemia (contact)

Factors Influencing the Epidemiology of Zoonoses: 

Factors Influencing the Epidemiology of Zoonoses MIGRATION Animal reservoir movement, co-hosts that allow long term survival, overwintering birds, migratory patterns Tularemia: migrating Canadian muskrats in Vermont RMSF in the Bronx (?? Bird dropped tick)

Factors Influencing the Epidemiology of Zoonoses: 

Factors Influencing the Epidemiology of Zoonoses ARTHROPODS Pathogens ability to perpetuate in an arthropod host = vectorial capacity conditions affecting multiplication of arthropod and vertebrate host Lyme- deer, ticks, acorns, gypsy moths Asian tiger mosquito from used tire casings imported / stockpiled in Texas- vector for 22 arboviruses, spread to 25 states

Convergence of Factors: 

Convergence of Factors These factors may affect more than one disease: Malaysia has had outbreaks of the following in the last few years Leptospirosis enterovirus 71 encephalitis Chikungunya polyarthritis Nipah encephalitis

Example of a Zoonosis: Echinococcosis: 

Example of a Zoonosis: Echinococcosis Life cycle Epidemiology

Caused by a dog tapeworm…: 

Caused by a dog tapeworm… Affects many mammalian species Definitive host- canine carnivores, who pass infected eggs in their feces Intermediate hosts- pastoral: farm animals (sheep, cattle, swine, horses) Eat eggs with soil or vegetation→ hatches, →penetrates intestinal wall → lodges in viscera or lungs→ develops cysts→viscera eaten by canid… Humans usually incidental hosts but may be intermediate

People and herding dogs: 

People and herding dogs


Transmission: Egg ingestion (viable for days-years) Canine: wild or domestic Feces contaminate soil Sheep, caribou or moose (people): infected by grazing Hydatid cysts in viscera of intermediate host Canine eats contaminated entrails: adult form – eggs in feces

Echinococcus granulosus and Hydatid Disease (cont’d): 

Echinococcus granulosus and Hydatid Disease (cont’d) Distribution S. America Mediterranean South Central Russia Central Asia Australia Africa Distribution: Echinococcus granulosus

Echinococcus granulosus and Hydatid Disease (cont’d): 

Echinococcus granulosus and Hydatid Disease (cont’d) World: Prevalence 150 cysts/100,000 population in Uruguay & Argentina (CXR) 6-9% Peru/Andes (CXR +/- serology) Animals: 32% dogs, 89% sheep 2% Libya Hyperendemic area: Turkana/Kenya 198 cases/100,000 (surgical disease)

Epidemiology of Transmission: 

Epidemiology of Transmission Risk- proportional to how closely humans live with their dogs Turkana- sleep with dogs, dogs lick children clean, dog feces used as cosmetic, burial practices Beliefs may contribute to transmission Cysts in animals thought to be for water storage, thus desirable Giving viscera to dogs to consume after slaughtering

Alberta Data Reference: Somily, Miedzinski, Robinson and Marrie Poster P-785, 42nd ICAAC San Diego: 

Alberta Data Reference: Somily, Miedzinski, Robinson and Marrie Poster P-785, 42nd ICAAC San Diego Sporadic in Northern Canada and Alaska sylvatic variant Chart review of medical records ‘91-’01 N=42 22 definite/probable : 77% F, 50% Canadian 20 possible : 45% F, 70% Canadian born 28 hepatic, 11 pulmonary, 3 other 17/42 cases – First Nations ancestry Of sylvatic cases: 15 observed, 6 resected, 1 medical therapy, 7 combined therapy : 1 death

Echinococcus granulosus and Hydatid Disease (cont’d) : 

Echinococcus granulosus and Hydatid Disease (cont’d) Clinical manifestations and pathology Pressure effects of cysts on an organ/tissue, and unique to organ Onset: months to years Organ involvement Single vs multiple cysts Location Liver >Lungs> Other Cyst rupture - complications

Echinococcus granulosus and Hydatid Disease (cont’d): 

Echinococcus granulosus and Hydatid Disease (cont’d) Diagnosis by epidemiology… History of exposure/residence in endemic areas Mass on physical exam Radiography U/S CT, MR Fluid aspiration (+/- hydatid sand)

Other Treatment: No impact on transmission, however…: 

Other Treatment: No impact on transmission, however… Antiparasitic drugs (Albendazole / Mebendazole) ~25-35% recurrence Surgical removal up to 30% local recurrence try to prevent development of disseminated disease post rupture with Rx?

Is the Canadian epidemiology different?: 

Is the Canadian epidemiology different? Intermediate hosts documented: reindeer, caribou, moose and elk (not buffalo) Definitive hosts : dogs (up to 25% - 50% infected), wolves, coyotes Northern sylvatic echinococcosis said to have an excellent prognosis Meltzer,1956 (n=180) and Wilson, 1968 (n=101) and Finlay, 1992 (5 pediatric cases) Said not to cause anaphylaxis/seeding

Control: Discussion: 

Control: Discussion Treat the definitive hosts periodically Praziquantel to dogs Education don’t feed raw viscera to dogs, dog feces exposures Inspection of abattoirs Viscera handling, canine presence New Zealand, Tasmania, Cyprus, Argentina, Chile- have had success with control

Leptospirosis: A Worldwide Zoonosis: 

Leptospirosis: A Worldwide Zoonosis Leptospirosis zoonotic disease caused by a spirochete often related to occupation Humans are infected via contact with animal reservoirs (many species-e.g. rats, mice, or hedgehogs) contaminated environment (soil, sewage, or water) The clinical spectrum of the disease depends on the serogroup and the host mild flulike illness ranging to severe disease with multiple organ failure (Weil's disease)

An Australian Settlers Diary: 1866: 

An Australian Settlers Diary: 1866 ? leptospirosis “I was down last week three days with the fever & had the sandy blight badly at the same time. …the fever is no worse than a very bad bilious attack & sick headache only you have no power to move. It takes you as suddenly as if you were shot & leaves you as weak as a cat... “

Epidemiology of Leptospirosis: 

Epidemiology of Leptospirosis Leptospirosis occurs worldwide Infections are endemic in most temperate and tropical climates peak occurrence during or immediately following periods of high precipitation.

Epidemiology of Leptospirosis: 

Epidemiology of Leptospirosis Reliable surveillance data lacking clinical presentation is nonspecific and diagnostic capabilities are usually limited in countries with the greatest burden of disease Tropics: antibody prevalence rates to local may exceed 80%. In 1992, Hawaii reported an annual incidence of roughly 128 per 100,000 population using active surveillance.

Many Species Involved: 

Many Species Involved Leptospirosis is a disease of amphibians, reptiles, and mammals including humans Wild, domestic, or peridomestic animal infections, such as those occurring in rodents, livestock, and dogs, range from subclinical to symptomatic Infected animals may become reservoirs


Transmission Leptospires are excreted in animal urine become established in soil and water (survive for weeks to months) Contact with this soil or water- infection Humans and animals can also become infected by direct contact with infected animal tissues and organs.

Leptospirosis in Humans: 

Leptospirosis in Humans Occupational risk animal trappers and hunters, dairy farmers, livestock workers, abattoir workers, veterinarians, rice farmers, military personnel, and sewer workers. Recreational exposures wading, swimming, white-water rafting, canoeing, kayaking, and competitive swimming Disease M > F related to occupational and recreational activities.

Leptospirosis in Humans: 

Leptospirosis in Humans Epidemics of leptospirosis have been associated with flooding, tropical storms, and hurricanes Caribbean and Central and South America. Heavy rains increase human exposure to leptospire-contaminated groundwater (walking through streams, puddles) and soil Rains may also facilitate peridomestic rodent infestation

Animal Leptospirosis: Ontario Example: 

Animal Leptospirosis: Ontario Example Leptospirosis in dogs increased in 2000 The highest frequency of seropositive cases occurred from September to December 2000, with the peak in November The year 2000 was the warmest in Ontario in the previous decade Was also the third wettest in the fall period in the last decade

Leptospirosis Control: 

Leptospirosis Control Educate re: transmission- water exposure Protective clothes in hazardous work Drain contaminated waters where possible, or shut the pool! Rodent control, burn sugarcane fields before harvest ???Immunization- animals, humans Preventative doxycycline

Brucellosis: A Prototypical Zoonosis: 

Brucellosis: A Prototypical Zoonosis Undulant Fever, Malta Fever, Mediterranean Fever Systemic bacterial disease of domestic and wild animals with worldwide distribution High morbidity in humans- Fever, weakness, sweats, weight loss, localized infection of liver/spleen, also bone, joint, genitourinary: lasts days- months Bacteria persistently infect the animal host: Brucella abortus, Brucella melitensis, Brucella suis Diagnosed by microbiologic culture and serology

Brucellosis Epidemiology: : 

Brucellosis Epidemiology: Likely underrecognized/reported Worldwide, especially Mediterranean Europe, north and east africa, Middle East, India, Central Asia, Mexico, Central and South America OCCUPATIONAL: work with animals or tissues: farm workers, butchers, veterinarians Sporadic cases with consuming unpasteurized milk/products

Brucellosis Epidemiology:: 

Brucellosis Epidemiology: Eradication/control of bovine Brucellosis has reduced human disease in US, except for link with unpasteurized Mexican goat cheese


Reservoir/Transmission Cattle, swine, goats, sheep, yaks, camels, and occasionally elk, bison, caribou, deer Transmission Nonintact skin or mucosal contact with infected animal tissues, blood, urine, vaginal discharge, aborted fetuses, placenta (localizes in reproductive tissues) Ingestion of raw milk/milk products Airborne infection of penned animals, lab workers

Cultural /Regional differences: 

Cultural /Regional differences Saudi Arabia : national human seroprevalence 15% Brucella melitensis clinical disease incidence in humans is close to 40 cases per 100,000 the Kingdom annually imports a few million heads of sheep and goats (for sacrifice during Hajj) from Africa, India, and Australia uncontrolled importation of animals that are poorly screened: Control program needed

Control: Discussion Points: 

Control: Discussion Points Considerations: Education/cultural practices recruitment and training of qualified veterinarians development of an adequate number of animal quarantine centers implementing legislation to control marketing and movement of animals.


Prevention Education re: unpasteurized dairy products Abattoir / slaughterhouse / hunter safety education (ventilation) Educations re: tissues – aborting animals Test livestock (ELISA)- segregation or slaughter of infected Immunize young sheep/goats PASTEURIZE MILK PRODUCTS!!!!

Trouble from Ticks: Lyme Disease: 

Trouble from Ticks: Lyme Disease

Lyme Disease: 

Lyme Disease Caused by tick borne spirochete Borrelia burgdorferi Most common vector borne disease in the US Recognized in 1975 by cluster of cases in Lyme, Conneticut of “juvenile rheumatoid arthritis”….three stage illness Localized Disseminated Persistent persistent disease arthritis, neurologic system, skin spread to skin, heart, joints, nervous system Characteristic rash

Lyme Epidemiology: 

Lyme Epidemiology 1-14 >=15* 0 1999

Lyme Epidemiology: 

Lyme Epidemiology After initial description Rapid increase in reported cases Geographic spread across the US Microenvironments, niches: remote sensing and geographic information system (RS/GIS) technologies to correlate specific ecologic conditions with outbreaks of infectious diseases specific vegetation and landscape patterns can be described and predicted by RS/GIS.

Lyme Epidemiology: Canadian Ticks: 

Lyme Epidemiology: Canadian Ticks In Canada the distribution of I. scapularis is uneven and focal (bird migration plays role) adult I. scapularis detected in low numbers in southern Manitoba, Ontario, the eastern townships of Quebec, Nova Scotia, New Brunswick, PEI, and Newfoundland at the present time, reproducing populations of I. scapularis are only known to be established on Lake Erie, Ontario.

Vector (Ixodid ticks ) and Hosts: 

Vector (Ixodid ticks ) and Hosts Adult ticks feed and mate on large animals, especially deer, in the fall and early spring Female ticks then lay eggs on the ground and in summer, eggs hatch Larvae feed on rodents and birds in the summer- fall inactive until the next spring when they molt into nymphs. Nymphs feed on small rodents and birds in the late spring and summer and molt into adults in the fall, completing the 2-year life cycle. Ticks typically become infected with Lyme disease bacteria when they feed on infected small animals, particularly the white-footed mouse The bacteria remain in the tick, which transmits Lyme disease bacteria to other small rodents, other animals, and humans with subsequent feeds

Lyme Ecology: 

Lyme Ecology Ticks must attach >24h for disease transmission Deer not involved in lifecycle of the spirochete but are important for the ticks West coast: nymphal ticks prefer lizards which do not support infection: lower rates Ticks feeding on birds may account for geographic spread

Lyme Issues: 

Lyme Issues Clinical diagnosis of early disease quite good (characteristic skin lesion) Late Lyme arthritis and encephalopathy can be difficult to distinguish from difficult to clarify syndromes such as fibromyalgia Dx: clinical picture, EXPOSURE, and serology for antibody response Antibiotics are effective in the first 2 stages of disease

Control of Lyme Disease: 

Control of Lyme Disease Prevention: Public Education re: tick avoidance/removal Tick control: not practical for large scale ? Deer control Permethrin cotton balls for mice nesting??? Vaccine: 76-83% effective ?duration Who to vaccinate?? 15-70 y old, outdoor exposures, high prevalence areas Control of Patient, Contacts, Environment- Not necessary/feasible


Conclusions Zoonotic diseases are rare (or at least uncommon) individual causes of morbidity and mortality BUT contribute very significantly as a group to human disease Knowing the complex ecology of the hosts, vectors and pathogens is essential in the clinical and epidemiologic understanding of these diseases

Final Word on : 

Final Word on Google search – first hit is “Daniel Shapiro’s Zoonosis web page” Gives this definition: “A zoonosis is a disease that humans may acquire from animals. For every cute, cuddly (non-human) creature out there, there is something horrible that you can potentially catch from it.”

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