|Barked: Wed Jan 14, '09 2:54pm PST |
|Hi everyone. I will add some info here on this subject that hopefully will help. Though I'm not yet a licensed DVM I'm working on it and having just finished the parasitology course in my curriculum I suppose I probably should know a thing or two about hookworms. However, as the generic response goes "always consult your veterinarian"
Most of the information posted above is pretty accurate. One small correction is hookworms have never been shown to cross the placenta in dogs or cats and only in dogs are they documented as passing via nursing. Like roundworms, depending on the route of infection (i.e. ingested an infective larvated egg, eat a rodent, or in the case of hookworms, through the skin) the larvae 'migrate' through the body in a variety of ways eventually finding their way to the small intestine where they become adults. No matter how they became infected, it is inevitable that some larvae undergo what is called "somatic" migration in which the larvae become encysted in other tissues of the body and lie dormant. Sometimes for life and then, for no apparent reason, sometimes they can 'awaken' and finish progression. In the case of females, pregnancy will cause this, hence the reason all puppies are born with roundworms and subsequently get hookworms after nursing.
It is rare to ever find an adult worm in feces except in extreme conditions because they are in the small intestine but as they die they can be passed. In the case of whip worms though, as they live closer to the 'end of the line', perhaps, but they are pretty small.
It was mentioned that wherever dogs are, these parasites will be found and that couldn't be more true. Eating poo is the most common source for dogs, but even the grass the poo was on may have eggs in it, however for both round worms and hook worms, for the dog to become infected, the eggs have to 'larvate' in the environment. ~month for round worms, ~2-7 days for hooks, or else they'll just pass right through the dog. Round worms take 3-4 weeks and Hook worms 4-5 weeks to become adults to the point we can detect eggs in fecal exams.
Herein lies a problem within many veterinary practices. I am not challenging your veterinarian's expertise nor meaning to offend but the old method of fecal loops and testing a minute portion of fecal material via saline and coverslip is not terribly accurate as far as detecting infections. They do work, IF they are able to get a large amount of fecal material in the loop AND there is a patent infection where many adults are shedding many eggs. So take a 'negative' fecal exam with a grain of salt. All it means is no eggs were observed. Semantics...I know, however this can lead to misconceptions of if the medications you are using are working.
In Henry's case, it's possible that subsequent reinfections are occuring on the walks through the woods, especially down by the river where the free living larvae that would penetrate the paw pads would love to be but doubtful this time of year. The species of Ancylostoma in Henry's area might actually be Uncinaria which is the northern form and the eggs resist freezing. In any case, if Henry has been infected, his backyard is contaminated and the best prevention is doing what you already are...picking up the poo.
The dogs are not getting hookworms from eating cat poo. Ancylostoma sp. are pretty host specific except in the case of one particular species that I do not believe is found in the US. They will infect rodents and yes, even humans but you can consider A. caninum limited to dogs, A. tubaeformae to cats.
The monthly dewormers (often combined with Heartworm preventatives) are often misunderstood as 'preventatives' which is incorrect. They merely kill adults. Given once a month, they basically 'reach back' and kill any adults that have arrived at the final maturation point in the small intestine in the last 30 days. There most likely are more larvae in migration that will arrive after the monthly dose you give wears off 3 days or so after you give it. Migrating larvae are unaffected by dewormers. This often leads to return visits to the vet with complaints that the meds just aren't working. Heart worms are a whole different ball of wax and I'll not bore you with those details.
Panacur C was mentioned as having been used. The drug in it is fenbendazole instead of milbemycin oxime (Interceptor). Both effective vs. rounds, hooks, whips but the difference is (besides $$$) Panacur is given more frequently and orally which gives it the advantage over topical applications given once a month. All the drug manufacturers have gone to great lengths to validate the efficacy of their products so they can have the coveted "FDA approval" label and resistance is not an issue (yet) as it is in large animals.
IF it appears the drugs you are giving just aren't doing the job even though you are giving the dewormer like clockwork and doing everything to prevent reinfection, try switching from Interceptor to Heartgard Plus or talk to your vet about a moxidectin injection. Both are more effective against Uncinaria sp. of hookworms which is very possible in northern climates. The eggs are nearly identical so your veterinarian really has no way of distinguishing the difference with much certainty.
One huge myth I want to address is that by not treating the infection it allows the dog to develop immunity. This is 100% false in the case of small animals. The immune system has a role, but immunity is never achieved. These parasites cause damage to the small intestine, and in the case of hookworms, they feed on blood. Severe infections can kill a dog by a variety of means: anorexia, blockage, anemia to name a few and a puppy could die within days if the bitch has a severe infection herself. Not to mention this allows the dog to contaminate the environment for years with eggs passed in the feces and worse yet, since there is free form larvae involved with hookworms, it increases the likelihood of human infections.
I hope this information helps and certainly is not meant to contradict anyone's personal veterinarian or specific treatment/prevention guideline he or she has prescribed. Always pick up the poo and never play with raccoons!!!
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