Practitioners need to consider different approach for parasite control in kittens

Parasite control in kittens requires knowledge of the pathogens involved and the capabilities of the different products for controlling the parasites of interest. This article will review the parasites and their mode of transmission to kittens. It will then examine the various products available for parasite control in kittens. Also, it will look at kittens as potential sources of agents of zoonotic importance. Finally, it will examine various means of ensuring that kittens are protected from these infections.

Adult female earmite, Otodectes cynotisaption, can be directly acquired by kittens from their mother.

Internal parasites

Kittens acquire only a few internal parasites from the queen directly. The only common internal parasite that is acquired from the queen after birth is the common feline roundworm Toxocara cati, which is transmitted to the kittens in the milk. It is unclear when the kittens will first shed eggs in their feces after transmammary infection, but it seems that the first eggs would be shed no earlier than one month after birth. Kittens can acquire congenital toxoplasmosis from the queen, but it appears that this is most likely if the queen is infected for the first time while pregnant. Congenitally infected kittens appear to develop disease but do not appear to shed any significant number of oocysts. The relatively rare intestinal fluke, Alaria marcianae, can infect kittens via the milk of the queen, but these infections are seldom life threatening, and eggs in cat feces pose little risk to owners because an intermediate host is required in the life cycle of this parasite. There is neither transmammary nor transplacental infection of kittens with the feline hookworms, Ancylostoma tubaeforme and Ancylostoma braziliense; thus, hookworms do not pose the same risk to kittens that Ancylostoma caninum poses to puppies.

Fleas can cause severe anemia and death in kittens, so it is essential that they be protected from these parasites.

Ectoparasites

There are a number of ectoparasites that kittens can acquire by direct contact with the queen as she cares for them. These include: fleas (Ctenocephalides felis), lice (Felicola subrostratus), ear mites (Otodectes cynotis), mange mites (Notoedres cati), and the fur mites (Cheyletiella blakei and Lynxacarus radovskyi). Thus, kittens, when nursing, are at risk on becoming infested with some of the insect and arachnid pathogens that are present on the queen. Only two of these pathogens are common in cats, fleas and ear mites, so the risk of kittens acquiring infections with these other pathogens is rather rare. Also, with the exception of fleas, these pathogens are typically not life threatening to kittens. Fleas on the other hand, can cause severe anemia and death in kittens, so it is essential that they be protected from these parasites. It is also believed that flea feces are the source by which cats are infected with the cat-scratch fever agent, Bartonella henselae; thus, this is another reason to keep cats free of fleas.

Table 1: Antiparasitic products for cats and their label claims

Direct transfer to kittens via feces can occur with respect to a few parasitic pathogens. Queens shedding Giardia felis or Cryptosporidium felis in their stools can directly infect young nursing kittens. In a similar fashion, they can infect kittens with intestinal trichomonads. The only helminth that would be directly infectious to kittens is the stomach worm Ollulanus tricuspis, which is transmitted in feces or vomitus; but fortunately, Ollulanus tricuspis is only relatively rare in cats.

Other risk factors

There are a number of fecal stages passed by queens that are capable of developing in the environment rather rapidly and infecting kittens soon after birth. The most common of these pathogens would be the coccidians, Isospora felis and Isospora rivolta, which can cause disease in neonatal kittens. Infective stages of these parasites could appear in the feces of cats as soon as a week after birth. Also, the other roundworm that infects cats, Toxascaris leonina, has an egg that rapidly develops to the infective stage, and it can often infect cats while they are still quite young, although it will take about two months before eggs would appear in the feces of the kittens. If hookworm eggs are shed by the queen into a warm moist soil environment around the kitten, infective-stage larvae could develop and be a source of neonatal infection in kittens. Kittens could contaminate the environment with hookworm eggs as soon as two weeks after birth, but more likely not until they were about 4 to 6 weeks old. (They would need to move about in the contaminated soil to get infected, and it would take two weeks for the worms to mature.)

Table 2: Age of first administration of antiparasiticides labeled for cats

There are two parasites that can be important in kittens and which infect cats through arthropod vectors. The flea tapeworm, Dipylidium caninum, infects kittens if they ingest infected fleas. The kittens can shed segments within three weeks of having eaten the flea, and it is possible that large numbers of these tapeworms could cause impaction of the small intestine. Kittens also can be infected with heartworms by mosquito bites, but it is unclear how often this is an important disease in very young animals.

Eggs of Toxocara cati. Kittens need to be protected against roundworms and other parasites to avoid serious medical problems.

Treatment and control

The products that control parasites in cats only are effective against a very few of the parasites previously listed. Infections with giardiasis, coccidiosis, cryptosporidiosis and toxoplasmosis will be treated using various off-label combinations of products or through the use of various palliatives for the signs of infection. Similarly, the rare nematode or trematode infection will be treated only when diagnosed. Control programs have to be targeted at the common parasites. Thus, the available products labeled for parasite control in cats treat or control infections with roundworms, hookworms, heartworm, tapeworms, fleas and ear mites (Table 1, p. 14). Frontline® Plus provides broad-spectrum protection against ticks and protects against adult fleas and also has effects against the developing larval stages of fleas. Advantage™ protects cats against adult fleas. These products differ as to the time they can be first administered to kittens (Table 2), and it should be noted that one of the most common products for treating hookworms and roundworms in kittens, pyrantel pamoate, does not appear on the list of labeled products for cats. Thus, the standard of treating kittens with Nemex or Strongid T (at 20 mg pyrantel pamoate per Kg of body weight), is an off-label use of both products.

Kittens pose less of a risk of zoonotic transmission than puppies because they are not infected with zoonotic agents prenatally. Thus, the Centers for Disease Control and Prevention (CDC) recommends that kittens be treated every two weeks beginning the third week of life, with treatments at 3, 5, 7 and 9 weeks of age (The CDC suggests puppies begin treatment at 2 weeks of age.). It should be noted that piperazine, which does not kill hookworms, is the only product labeled for administration to cats at the age of 3 weeks. Thus, none of the labeled products are approved for the suggested age of first treatment. Also, given the excellent potential control of internal and external parasites in cats by the administration of the broad spectrum or combination products, it seems worthwhile to build these products into the control program for kittens because they have been looked at relative to the safety of repeated administration. Any such program could be supplemented with Drontal as needed to provide roundworm and tapeworm control. Again, it is essential that kittens be protected from fleas.

Table 3: Treatment of kittens with additional products if beginning at 6 weeks of age on one of the broad-spectrum products that also prevents heartworms

Thus, the first thing to do is to ensure that the queen is already on some form of flea control to protect the neonates from fleas. (She should also already be on some form of internal parasite control program.). Then, if it is deemed necessary to treat cats early in life, they could be treated at 3 weeks and 5 weeks of age with Drontal. (This is a week before the labeled first treatment at 4 weeks of age, but there is no reason to believe that the pyrantel and praziquantel in these tablets would hurt the kittens). Drontal will remove hookworms and roundworms like pyrantel, but will also prevent any infections of cats with Dipylidium caninum. Then, at week 6 or 8, the cats could start on one of the monthly products that have been tested as to their safety for repeated regular administration (Table 3). Cats could be treated with Drontal during the third, fifth and seventh week of life and then started on Revolution® on week eight. If a cat begins on Heartgard®, it will be necessary to continue treatment with Drontal on weeks seven and nine to ensure roundworm control. If a cat begins on Interceptor®, additional internal parasite control is probably not necessary. Flea control in Heartgard or Interceptor® cats could begin with Program® at the time of first administration of the monthly product, or it could begin at eight weeks with Frontline® Plus or Advantage®. If kittens are noted to be infested with fleas, they could be treated with Capstar® beginning at four weeks to remove the adults. If ear mite treatment is needed for the Heartgard or Interceptor cats, it could be provided with Revolution, Acarexx or Milbemite. Tapeworms can be treated with Drontal, Droncit, or Cestex if they are diagnosed. Revolution and Frontline both probably have effects against mange and fur mites, and these two products and Advantage probably all have efficacy against the feline louse, Felicola subrostratus.

Suggested Reading

Thus, it should now be relatively easy to develop a program that will prevent infections with parasites in kittens and provide assurance to owners that there cats are not going to be sources of potentially zoonotic parasites. Any control program needs to be backed up with regular physical examinations and with regular fecal examinations. Kittens are going to continue to get sick from a number of protozoan parasites, and perhaps, someday, it may be possible to also protect kittens from these agents.

Dr. Bowman received a master's degree and a doctorate in parasitology from Tulane University. He joined the faculty at Cornell University in 1987 as an assistant professor of parasitology. In 1993, he became an associate professor. Dr. Bowman has also worked as a research associate at the University of Wisconsin School of Veterinary Medicine.

Dr. Bowman has special interests in soil-transmitted parasites, soil-parasite interactions, nematodes, especially ascaridoids, apicomplexan protozoa and zoonotic diseases, parasites of wildlife.