Zoonosis

Question 1

What is zoonosis

Answer 1

any disease or parasite that is transmissible from animals to humans
disease of animals that can be transmitted to humans
risk of infection to members of the general population is usually very slight
However, people whose employment brings them into contact with animals (laboratory facilities, intensive livestock operations, and kennels) or animal products (slaughterhouses), or whose job it is to diagnose diseases of animal origin, should be more aware.

Question 2

Cutaneous larval Migrans or “creeping eruptions” are caused by

Answer 2

Ancyclostoma spp. (Hookworm)
Strongyloides stercoralis (dog threadworm)

Question 3

Why do cutaneous larval migrans happen from dog threadowrms

Answer 3

People are infected via skin penetration by infective L3
Linear tortuous, inflamed, and intensely pruritic lesions of the skin caused by the penetration and migration through the skin (usually on the feet) of infective larval stages (L3)
People become infected by walking barefoot on beaches or in parks and yards where dogs have defecated, or by lying on damp contaminated soils or beaches
Strongyloides will eventually migrate to the intestine and mature. Canine hookworm will not.
Prevention: quick removal and safe disposal of feces and wear shoes!!

Question 4

Visceral + ocular larval migrans and toxocariasis are caused by

Answer 4

Toxocara canis and T. cati (Ascarids/Roundworms)

Question 5

What does Toxocara canis and T. cati (Ascarids/Roundworms) do to people

Answer 5

People can act as an accidental paratenic host and larvae will undergo somatic migration, causing visceral and/or ocular larval migrans.
The eggs, containing infective third-stage larvae, are ingested by a person and the larvae hatch and migrate.
People are not the normal definitive host – therefore migrating larvae end up a bit “lost”. They may end up in various tissues including muscle, organs, brain and eye (ocular larval migrans), causing a wide variety of clinical signs from nothing to malaise, fever, vague abdominal pain, coughing, granulomatous retinal lesions potentially leading to blindness.

Question 6

How do people get aylisascaris procyonis (Racoon Roundworm)

Answer 6

Spread by raccoons
Exposure to racoon latrines
human ingestion of infective eggs containing third-stage larvae may lead to a fatal invasion of the brain by the larva known as neural larval migrans.
Do not keep raccoons as pets

Question 7

how do people get A.suum and what does it do

Answer 7

Ascaris suum will happily complete its life cycle in people (DH).
Infected by ingesting egg with L3
Lab workers, garden fertilizer, chicken livers
Ascaris lumbricoides

Question 8

Life cycle of Trichinella spp. Trichinellosis within people

Answer 8

Infection is by ingestion of muscle tissue cysts containing larvae. (carnivory)
The larvae are freed when the cyst wall is digested in the stomach and the larvae enter the mucosa of the SI.
There, they develop into adults, mate, and the females release larvae (adults soon die).
The larvae migrate into the lymphatics and travel through the portal system to the circulation, and out to the striated muscle.
There, they enter a muscle cell and grow, coiling in the cell. They form a capsule which protects the larva.
Larvae do not develop any further until ingested by the next host
Each host acts first as a definitive host and then become essentially an intermediate host with larvae in muscle tissue.

Question 9

How do people get T.nativia and trichinella spirallis and what does it do to people

Answer 9

Trichinella spiralis, T. nativa and other freeze resistant species
This parasite is often associated with the consumption of undercooked pork (T. spiralis)
Freezing, cooking properly
Smoking and drying (jerky) will not kill the parasite-
This species is now only very rarely seen in Canada – the commercial pork herd is considered Trichinella free.
These days people are usually infected by eating undercooked wild meat, especially bear and walrus (T. nativa and other species).
Cooking
Freezing, smoking, fermentation and drying will not kill the parasite
In wildlife and domestic animal hosts there are no detectable symptoms
In people, it can produce a very serious illness (potentially deadly)

Question 10

What are the clinical findings with Trichinella spp in people

Answer 10

In people, it can produce a very serious illness with symptoms including diarrhea, skin rash, fever, abdominal pain, malaise, myalgia, periorbital oedema, leg swelling, vomiting and even death

Question 11

How do you diagnose Trichinella spp

Answer 11

May be suspicious if history of eating undercooked meat.
Biopsy of muscle tissue,
ELISA (serology) can detect anti-Trichinella antibodies (but not until several weeks after the infection).
tissue digestion (muscle of domestic and wild hosts)
Surveys of wildlife can tell us where the parasite is present and what percentage of a population is infected (example; walrus in Quebec)

Question 12

How do people get Diphyllobothrium latum (Broad Fish Tapeworm) and what happens to people

Answer 12

People are the definitive host and get infected by ingesting plerocercoids from undercooked fish.
People that have been treated have eliminated several hundred feet of tapeworm (numerous adults infecting an individual).
Can be up to 12 m long and can live 10 years in host
Rarely symptomatic but reports of anemia as the parasite selectively uptakes VitB12.

Question 13

How do people get Dipylidium caninum (Cucumber seed Tapeworm) and what are the signs

Answer 13

Humans infected by ingesting an arthropod(flea or maybe a louse) containing a cysticercoid
Infected individuals may show nocturnal irritability, anorexia, weight loss – particularly in children.

Question 14

How do people get Echinococcus canadensis (E. granulosus) (Cystic Hydatid Tapeworm) and what happens

Answer 14

Single large cyst, covered by a fibrous capsule
People act as the intermediate host in this infection after ingesting an egg containing a hexacanth larvae
In people cysts can get as large as 50 cm diameter and contain 16 L of fluid
If they rupture; cyst fluid can cause severe anaphylaxis and death
In the human host,cysts develop mainly the liver or lung but possibly brain and does its damage as a space occupying lesion

Question 15

How do people get Echinococcus multilocularis (Alveolar Hydatid Tapeworm) and what happens to them

Answer 15

People act as the intermediate host in this infection after ingesting an egg containing a hexacanth larvae
Produces a multilocular cyst composed of multiple, thin-walled vesicles, these can grow in place, usually the liver, and they may expand in a highly invasive manner.
May also metastasize to other places in the body including lungs and brain
Mortality rates of 50-70% in people
This is an emerging infection in western Canada

Question 16

What is the beef tapeworm

Answer 16

Taenia saginata (Cysticercus bovis, Beef Tapeworm;)

Question 17

How do people get Taenia saginata (Cysticercus bovis, Beef Tapeworm;)

Answer 17

With T. saginata people act only as the DH and acquire this infection when ingesting undercooked beef containing cysticerci

Question 18

What happens to people infected with Taenia saginata

Answer 18

This is a relatively harmless infection in people.
The parasite is observed occasionally in Canada and is most often detected in cattle at slaughter (cysts in muscle).
Most human cases in Canada have been acquired overseas
a positive animal is usually condemned and removed from the human food chain. There is also trace back and quarantine of the farm of origin, and an investigation of the extent of the problem on the farm and attempts to identify the source of infection, which is often very difficult. (promiscuous defecation)

Question 19

What is the lifecycle of Taenia solium (Pork Tapeworm, Cysticercus cellulosae) and where do people fall

Answer 19

With T. solium people are the DH (via pork ingestion), infection with the adult tapeworm is rarely pathogenic
Pigs are the IH – with cysts in muscle tissue
Prevalence tends to be higher where pork is eaten without appropriate cooking and/or where pigs can ingest material contaminated with human feces containing the T.solium eggs.
But people can also act as a IH with cysticeri in various muscles and tissues. We acquire this infection if we ingest T. solium eggs (maybe crops fertilized with human manure)
But; an infected person may auto-infect; That is, they have adult tapeworms in their SI, tapeworm eggs may hatch in the LI or may leave the host but be accidentally ingested. (food contamination if hands are not properly washed)

Question 20

What happens to people infected with Taenia solium (Pork Tapeworm, Cysticercus cellulosae)

Answer 20

These eggs, however acquired, hatch in the stomach and SI, the larvae will migrate to muscle and maybe neural tissue and develop into cysticerci.
Depending on the location of the cysticercus in the intermediate host, clinical signs range from asymptomatic(most often) to blindness and seizures
This In Canada, human infection is generally thought to be acquired outside the country. Cysticercus cellulosae has not been detected in pigs in Canada for many decades, and is assumed not to occur

Question 21

Cryptosporidium spp (Cryptosporidiosis; Apicomplexan protozoa – one of the coccidia) infects human how

Answer 21

Human infection is acquired via the ingestion of immediately infective oocysts, generally in contaminated food or water
Most often human to human passage, but zoonotic transmission does occur (dairy calves)

Question 22

What are the signs and treatments with Cryptosporidium spp

Answer 22

General GI signs include anorexia, weight loss, watery diarrhea, abdominal pain, and tenesmus; can be subclinically infected
NO EFFECTIVE TREATMENT. Self-limiting disease in immunocompetent individuals, therefore provide supportive care
This infection can kill immunocompromised individuals

Question 23

Giardia in people is gotten by

Answer 23

People acquire the infection via the ingestion of cysts, primarily from contaminated water or food.
most human cases of Giardiasis will have been contracted from a human source of contamination
dogs and cats may acquire a human strain of Giardia and then act as a reservoir of infection for humans although this is rare

Question 24

What are the symptoms of Giardia in people

Answer 24

Symptoms vary from none to severe diarrhea, abdominal cramping, and nausea may accompany an acute case.

Question 25

What does toxoplasma gondii cause

Answer 25

Toxoplasma gondii is also a significant human pathogen around the world
Some surveys up to 30% of the population have antibodies
infections in immuno-competent people, Toxoplasma usually causes only a transient flu-like illness with fever, malaise and enlarged lymph nodes… But…
In people and in animals, recent evidence suggests that subclinical infections with T. gondii might influence mental development, as well as risk-taking behaviours
Ocular disease
Congenital infections can result in abortion, stillbirth or lesions in the central nervous system, especially the eyes, depending on the timing in gestation. It may also lead to learning difficulties

Question 26

Sarcoptes scabiei is given to people how and what are the signs

Answer 26

Each host has its own variety, but there can be some transmission between hosts. Usually infestation is via direct contact.
Human infestation from an animal source can be very itchy but is generally short-lived.
May be some local allergic reaction to aggravate the condition