Zoonoses from Carnivores

Question 1

What type of parasite is Toxoplasma gondii?

Answer 1

apicomplexan protozoan parasite.

Question 2

When are cats usually infected with T. gondii? How long do they shed for?

Answer 2

Usually infected early in life, and excrete the oocysts for 1-3 weeks.

Question 3

Which immature stage of T. gondii replicates fast? Which replicates slow?

Answer 3

Fast = tachyzoites. Slow: bradyzoites.

Question 4

What behavioral change are you likely to see in mice infected with T. gondii?

Answer 4

They lose their fear of cats.

Question 5

How do humans become exposed to T. gondii?

Answer 5

by coming in contact with oocysts in soil, or by ingesting tissue with bradyzoites (undercooked meat for example)

Question 6

How long do oocysts remain stable in the environment?

Answer 6

18 days.

Question 7

How can you render tissue cysts noninfectious?

Answer 7

freezing for >7 days, or by cooking.

Question 8

Most human infections of T. gondii in the states come from what?

Answer 8

cumulative lifetime exposure to undercooked meat – NOT soil exposure.

Question 9

What does T. gondii cause in early pregnancy? What about in late pregnancy?

Answer 9

early - abortion/stillbirth. Late - baby born w/ toxoplasmosis. Will see hydroencephalis, blindness, etc.

Question 10

Does it matter when mom is infected with T. gondii while pregnant?

Answer 10

YES. The earlier she is infected, the more severe the symptoms for the baby when born.

Question 11

If a pregnant woman was infected with T. gondii prior to being pregnant, and becomes reinfected while pregnant, is this a problem?

Answer 11

No. Only a problem when infected for the first time when pregnant.

Question 12

How can a pregnant woman prevent exposure to T. gondii if she has a cat?

Answer 12

Clean the box every single day.

Question 13

What are some common roundworms of pet animals?

Answer 13

T. canis, T. cati, T. vitulorum

Question 14

What disease is considered a “neglected tropical disease”?

Answer 14

Human toxacariasis.

Question 15

Who is most at risk for human toxocariasis?

Answer 15

Children between the ages of 1-4 years, due to pica and geophagia (kids are gross, basically).

Question 16

What percentage of raccoons have Baylisascaris procyonis? Why is this of concern?

Answer 16

70-90% have it. Concerning because they shed a lot when they have it and it is very zoonotic (dogs can be definitive hosts or intermediate hosts).

Question 17

What is the most common form of larval migrans of Baylisascaris?

Answer 17

ocular or neurologic.

Question 18

For what cestodes do humans serve as the definitive host?

Answer 18

T. saginata and T. solium, Diphyllobothrium, Dipylidium caninum (rare).

Question 19

For what cestodes are humans an intermediate host?

Answer 19

Echinococcus granulosus and multilocularis, T. solium, and a few others that are rare.

Question 20

What are the symptoms usually like when a human is the intermediate host for a cestode infection?

Answer 20

symptoms are caused by the cyst, and clinical signs depend on where the cyst is (liver, lungs, brain, etc.). Can get anaphylactic symptoms if the cyst ruptures.

Question 21

What is the difference between hydatid cyst disease and alveolar cyst disease?

Answer 21

Hydatid cyst disease is caused by E. granulosus, and it is individual, large, fluid filled cysts in multiple tissues. Alveolar disease is made of multilocular small, and solid cysts.

Question 22

Who is the reservoir for all echinococcus species?

Answer 22

canids.

Question 23

How do humans get Echinococcus granulosus?

Answer 23

by ingesting the eggs, NOT MEAT.

Question 24

Cystic echinococcosis is associated with what industry in the US?

Answer 24

The sheep industry.

Question 25

Why is alveolar echinococcosis very destructive and often fatal?

Answer 25

because the cysts aren’t encapsulated and are very infiltrative, so they are often not operable once diagnosed.