Re: Man,Dog and Toxocara canis

Jennifer Mansfield-Jones (
18 Mar 1995 18:04:00 GMT

In article <3jqiq1$>,
Forest J Rushay <> wrote:
>For one thing, the parasite inhabits the lower alimentary tract, not the muscle
>(how many humans are hungry enough to eat dog entrails/excrement?)
>Secondly, how do you know humans CAN'T (or don't) carry canine roundworm?

I don't claim to be an expert on the topic, but what I've read
indicates that the few reports of human intestinal infections with
Toxocara canis (and similarly with Toxocara cati) in which the worms
actually matured may or may not have actually been Toxocara.

However, human infection with Toxocara larvae isn't all that unusual.
The problem isn't eating dog intestines, it's eating something
contaminated with T. canis eggs from dog feces. The infection is usually
asymptomatic, and I've seen one claim that about 3% of the people in the
US have had it at one time or another.

>ROBIN E WALKER <> wrote:
>>Whilst considering the evolution of the domestic dog and ,in
>>paticular, its employment as a food source by Man, I was struck by
>>the notion that the life history of Toxocara canis might tell us
>>something about the "dietary" relationship. It seems odd that the
>>somatic migration of toxocara larvae in paratenic hosts should
>>apparently be a dead end. But if eating dogs was common and access
>>to human remains by the dog (prior to burial customs, or as a
>>result of cannabilistic waste) was equally common, might the
>>lifeycle and behaviour of this parasite make more sense (if you will
>>pardon the teleology)? The other paratenic host species presumably
>>got variously butchered and eaten around the dumps and habitations
>>of Man by both man and dog.
>>I have questioned veterinary parasitologists but obviously the
>>concept is novel to them and the veterinary literature has nothing
>>to yield.

It *is* sort of interesting to contrast the situation in
Toxocara with Echinococcus granulosa (a dog/wolf tapeworm). There,
of course, humans make just as good an intermediate host as sheep
or elk do, with occasionally nasty results.

By a sort of bet-hedging argument, there might be a slective advantage
for a parasite with a complex life cycle to be a generalist with respect
to intermediate hosts.

In the unlikely event that the Jennifer Mansfield-Jones
Biology Department has an
official opinion, this isn't it.