Zoonoses from Milk and Water Flashcards
What are the (3) classic milkborne pathogens?
Mycobacterium bovis
Brucella
Coxiella burnetti
How do pathogens get into milk?
Bacteria infect the animal systemically and colonize the mammary glands
Bacteria can be secreted into milk in a chronic fashion, often with minimal symptoms in the animal
In addition to milk, there can be _____ transmission to people
Direct
Percutaneous or mucous membrane contact with infectious fluids
Aerosol exposure
Who are most at risk for zoonotic infections from organisms in milk?
People who work with infected animals or premises are at highest risk : farmers, veterinarians, and abattoir workers
T/F: Some imported soft cheeses are not pasteurized and therefore, have potential for zoonotic transfer
TRUE
Where do most cases of M. bovis occur?
Countries without pasteurization of milk or control programs in cattle
Pulmonary TB (M. bovis) cannot be discriminated from M. ________ via skin testing or x-rays, only by ________.
M. tuberculosis
culture
What percentage of “M. tuberculosis” cases in countries that do not pasteurize milk or test cattle are actually M. bovis?
10-30%
What are the 3 major zoonotic transmission routes of mycobacterium bovis?
Aerosol (from infected cattle to other cattle and to people who work with cattle)
Oral exposure: to milk, feces, LN contents
Percutaneous exposure: abattoir workers, necropsy, etc
How can M. bovis be controlled?
Eliminate the animal reservoir
Milk pasteurization
What clinical signs might you see in a person with Brucellosis?
aka “undulant fever” or “malta fever”
- recurring fever, can last for months
- abortions can occur if pregnant
- Pleiomorphic symptoms: neurological, endocarditis, possibly chronic fatigue
What is the causative agent of Q Fever? What signs might you see in a human infected?
Coxiella burnetii - causes a non specific febrile illness
Abortions if pregnant
Chronic pleiomorphic symptoms
May also present as atypical pneumonia or hepatitis
What is the most pathogenic species of brucella in people?
Brucella melitensis
It infects a variety of animals and is mostly found in the Mediterranean and other intensive goat-farming regions
What brucella species is highly pathogenic in people, and has a worldwide distribution (with the exception of places with successful eradication processes)?
Brucella abortus
Seen in cattle, bison, buffalo, horses, dogs etc
What two brucella spps are the least pathogenic in humans, but still a zoonotic concern?
B. suis and B. canis
How do people get infected with brucella?
Ingestion, mm exposure , or percutaneous inoculation with: aborted placenta, fetus or fetal fluids, unpasteurized milk, blood, urine, semen, feces, and vaginal secretions
*feed/water contaminated with these materials
What methods are taken to control brucella?
Elimination of the animal reservoir
Reduce public exposure by pasteurization of milk and milk used to make soft cheeses
Is there an eradication program for Coxiella burnetti in the USA?
NO
Greater than 90% of dairy herds in the US have C. burnetii (20-30% of cattle are shedding at any given time)
The basis of pasteurization standards is based upon what pathogen?
Coxiella burnetti
**this protects the public but not animal workers/farmers
How is C. burnetti transmitted?
***Aerosol exposure
Percutaneous and mm exposure
Is C. burnetti an environmental issue? Why or why not?
YES
It causes abortion - there are large amounts of pathogen in the aborted placenta and fetus: survives in water, soil, milk, and meat for WEEKS TO MONTHS
Chronically excreted in milk and feces (possibly urine)
What are some barriers to control?
Wildlife reservoirs
Social cost/veterinary infrastructure
Compliance of animal owners
What two protozoa pathogens pose a threat via water transmission?
Crypotosporidium
Giardia
How long can cryptosporidium and giardia survive in water if conditions are good?
MONTHS
T/F: Chlorinating water will prevent cypto and giardia
FALSE
**Must FILTER water
What spps of cryptosporidium is zoonotic and has cattle as the reservoir?
C. parvum
Outbreaks are typically rural
Often follow overflow/flooding of animal waste holding ponds or feedlot/dairy pens
What spps of crypto is transferred human to human - during outbreaks in urban municipal water systems?
C. hominis
Sewage tx does not always kill 100% of oocysts
What is the human infecting genogroup of Giardia?
A or B
T/F: Giardia in humans will typical cause acute intestinal infections
FALSE
giardia will cause chronic intestinal infections. Greasy, foul smelling dhr, weight loss
Who are the human amplifiers of giardia?
young children are better amplifiers than adults
Who will get severe dz from cryptosporidium?
immunocompromised people
How do people get infected with leptospira?
Usually from contaminated water: ingestion, via MM or broken skin contact
or via contact with infected animal urine
What clinical signs are associated with acute and chronic lepto infections?
Acute: fever, depression, lethargy, +/- icterus, headache/malaise, ocular pain in people, acute renal damage or failure
Chronic: large animal abortions, stillbirths, weak offspring, chronic renal insufficiency
What are some methods to reduce the lepto reservoirs?
Rodent control
treatment with antibiotics
Vaccines for animals (these include a limited number of serovars)
How can human exposure to lepto be reduced?
Ensuring a clean and treated water supply
Wearing gloves when handling urine and suspect cases
Who are the definitive host(s) and intermediate host(s) of trematodes?
definitive host - a vertebrate
intermediate - one or two; invertebrate arthropods or mollusks and fish
How does the definitive host of a trematode get infected?
Either by ingesting a cyst in or on food
How are accidental hosts of trematodes infected?
Percutaneously
What kind of trematode infection is more common in people, anthroponotic or zoonotic species?
Anthroponotic species
Some can have a secondary animal reservoir and function like zoonoses
Where does trematode disease typically occur?
Anywhere with appropriate water conditions and presence of intermediate hosts
*more common in tropical regions. Factors like flooding can increase risk
What is the second most important human parasite after Malaria?
Schistosomiasis
widespread in parts of Africa, South America, and south and southeast Asia
*some species are zoonotic- domestic animal reservoirs
What methods can be taken to control schistosomiasis?
Avoid swimming in fresh water
treat reservoir hosts
Kill intermediate mollusks
What is “swimmer’s itch”?
Skin lesions caused by the aquatic stage of bird trematodes entering humans (accidental hosts)
T/F: Humans can be infected with fasciola spp by ingesting infected beef liver
FALSE
How do humans get infected with fasciola spp?
Eating vegetables contaminated with metacercaria
ex: watercress
In what kind of environment would you expect fasciola spp?
marshy or low lying pastures
Cattle/sheep infected via vegetation near streams with infected snails
T/F: Fasciola spp are endemic in several parts of the US
TRUE
Which of the following cause bovine abortion and are zoonotic? (may be more than one)
- Brucella abortus
- Bovine viral diarrhea
- Trichomonas foetus
- Leptospira
- Coxiella burnetii
- Aspergillus fumigatus
- Listeria monocytogenes
Brucella abortus
Lepto
Coxiella burnetii
Listeria
