Lecture 16: Zoonotic Diseases Flashcards
Life cycle of taenia solium
- Porcine cysticercosis
- Pigs eat eggs
- Cysts in muscle - Human taeniasis
- Humans eat cysts in pork
- Adult tapeworm in GIT
- Not much pathology - Human cysticercosis
- Humans eat eggs
- Cysts in brain
- Neurocysticercosis
Neurocysticercosis in taenia solium
- Larvae encyst in brain
- Death in 50-80% w/o treatment
- Leading cause of seizure epilepsy in developing world
What drugs control seizures caused by neurocysticercosis
- Albendazole
- Praziquel
- Control in 80-90% of cases
Reservoirs of taenia solium
- Primary: people
- Intermediate: pigs
Taeniasis transmission to people
Eating undercooked infected pork
Neurocytosis transmission to people
- Self infection
- Faecal contam. from another person with an intestinal infection
- Consuming for or water contaminated with T. solium eggs
Prevention of human taeniasis
Target the vehicle
- Meat inspection
- Proper cooking and handling of raw pork (education)
Meat inspection only detects ____% of infested carcasses
50
Three ways to prevent human neurocysticercosis
- Block transmission (hand washing)
- Target the vehicle (sewage management)
- Target the reservoir (treat people with infections)
Prevention of swine cysticercosis
Target the vehicle (human sewage)
Giardia reservoir
many species
Transmission of giardia
- Consuming cysts
- Water most common
- Surface contamination of food
Prevention of giardia
- Water treatment (filtering)
- Sewage treatment, prevent contamination of irrigation water
- Wash or peel veggies and fruits
Two viral zoonotic diseases
- Rabies
- Hentavirus
Rabies
- Acute, progressive, encephalomyelitis
- Case fatality is highest of any conventional infectious disease
- One of the oldest described diseases
- Leading viral zoonosis in dual public health
Rabies is caused by RNA viruses in the family _____ and genus ______.
Rhabdoviridiae
Lyssavirus
Rabies host
- Most mammals are susceptible
- All reservoirs and vectors, not all vectors are reservoirs
Principle reservoirs of rabies
Carnivora
- Skunks
- Canids
- Raccoons
- Mongooses
Chiroptera
-Bats
Two forms of rabies
Furious
Dumb
Distribution of rabies
-All continents except antarctica
Rabies in the carribean
Caribbean mongoose
- Puerto Rico, Cuba, Dominican Republic, Grenada
- Evidence of bat rabies on Cuba, Grenada, and Trinidad
More than ______ human rabies deaths are estimated per year
50,000
Public health prevention for rabies
- Surveillance
- Reduce animal reservoir (vaccinations of domestics and wildlife)
- Reduce human risk (post-exposure procedures, vaccination of at risk individuals, education)
Where has dog rabies virus transmission has been eliminated where?
US
Bunyaviridae: Hantavirus
Enveloped ssRNA viruses
As a genus, distributed
world-wide
Reservoir of hantavirus
Rodents
Typically sylvantic but can infect pets
Rodent symptoms with hantavirus
asymptomatic
Rodents shed virus in
saliva, urine, feces
Transmission of hantavirus is primarily
Aerosol:
- Inhalation of viruses in urine or feces
- Virus survives for weeks in most bedding under cool conditions; susceptible to desiccation
- Transmission can be direct or indirect
Secondary transmission of hantavirus
Via bite
Severity of hantavirus in humans depends
On the species of the virus
Two clinical signs of hantavirus in humans
- Hantavirus Pulmonary Syndrome
- Hemorrhagic Fever with Renal Syndrome
Hantavirus Pulmonary Syndrome
- “New world” US disease
- Fever, chills, myalgia, headache
- Increased vascular permeability in the lungs
- Fatal 40% of human cases
Hemorrhagic Fever with Renal Syndrome
- “Old world” disease
- Petechial hemmorhage, renal damage, and cardiovascular shock=fatal up to 15% of cases
Risk factors for human transmission of hantavirus
Human rodent contact
- Increased rodent density
- People who work with rodents
Prevention of hantavirus
Reduce human exposure
Two types of zoonotic bacterial diseases
Anthrax
Brucellosis
Why can anthrax survive for years?
Spore forming bacteria
Anthrax affects herbivores who get spores by
ingesting spores in soil while grazing
Anthrax affects carnivores who get spores by
eating infected herbivores
All species get anthrax by
inhaling the spores in aerosolized soil or other soil or other contaminated from other contaminated fomites (Wool sorter’s disease)
How do veterinarians get anthrax
Aerosol or percutaneous exposure to blood from infected animals
Most veterinary cases of anthrax are seen in
cattle
Cattle anthrax
- Bleeding from all orifices
- Swelling
- Sudden death
Anthrax control from vets
- No necropsy on suspected cases
- Animal vaccination
- Burn infected carcasses or bury in quick lime
- Inform health officials
Doctors and public health for anthrax
- Work with vets
- Evaluate people post exposure
- Advise people to wash hands, then iodine solution immersion
What strain of brucellosis is most pathogenic to people
Brucella melitenis
What other animals does Brucellosis melitenis affect, and where is it mostly found
- Goats, sheep, caribou, reindeer, pigs dogs
- In Mediterranean and other intensive goat farming regions
What is the second most pathogenic strain of Brucellosis in people
Brucellosis abortus
What other animals does Brucellosis abortus affect, and where is it mostly found
- Cattle, bison, buffalo, elk, horses, dogs
- World-wide
What two strains of Brucellosis are less pathogenic in people
Brucella suis
Brucella canis
Brucellosis symptoms
- Recurring fever, can last for months
- Abortions can occur if pregnant
- Pleiomorphic symptoms (neurologic, endocarditis, possibly chronic fatigue)
- Difficult to diagnos without a good index of suspicion
Brucellosis is also called
- Undulant fever
- Malta fever
- Bangs disease
Transmission of Brucella
Ingestion, mucous membrane exposure, or percutaneous inoculation
- Aborted placenta, fetus, fetal fluids
- Unpasteurized milk
- Blood, urine, semen, feces, and vaginal secretions
- Feed/water contaminated with the above materials
Controlling Brucella
- Eliminate animal reservoir
- Monitor swine
- Reduce public exposure through pasteurization of milk
Two types of vector-borne zoonotic diseases
- Borreliosis
- West nile disease
How are Borrelia species transmitted
tick-transmitted spirochetes
Borrelia spp disease potential, geography, and reservoirs
- All have potential to cause chronic disease
- All have extensive geographical distribution
- All exist mostly in wildlife and occasionally spill over into pets and humans
Two types of Borrelia cause zoonotic diseases:
- Lyme disease = hard ticks
- Relapsing fever type = soft ticks
Lyme disease is vectored by… and reservoired by…
lxodes spp hard ticks
Sylvatic rodents and some lizards (NOT deer)
Lyme disease in people, dogs, and horses
Acute: -Febrile illness -Myalgia -Sometimes arthralgia -Possibly a bulls-eye rash Chronic -Cardiovascular -Neurological -Joints
For lyme disease, ticks must be attached for how long to transmit disease?
> 48 hours
West Nile genus
flavivirus
WNV is maintained through what cycle
Mosquito-bird-mosquito
- Primarily through Culex spp mosquito
- Birds maintain viremia for 1-4 days post exposure
WNV mortality in birds
- Most survive
- Has been detected in dead birds of >317 species
- Mortality mostly in crows, jays, ect.
WNV is primarily spread through
Bite of infected mosquitoes
No evidence that human infection occurs in handling ill or dead birds
WNV in humans and horses
Dead-end hosts
After infection with WNV,
host develops a lifelong immunity
Secondary transmission of WNV
Through bloodborne infection, lab exposure, breast milk
Clinical signs of WNV in horses
-Neurologic: ataxa, hypermetria, weakness, peri- or tetraparesis, recumbency death
Clinical signs of WNV in people
- Most (80%) are asymptomatic
- 20% develop a mild ferbrile illness
- 1/150 develop neuroinvasive disease (people >50 have highest risk and 10% of these are fatal)
