Revision for “Toxocara cati” created on August 12, 2015 @ 14:49:41
| Title | Toxocara cati |
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| Content | <p align="CENTER"><span style="font-size: medium"><i><b>Toxocara cati</b></i></span><span style="font-size: medium"><b> (Schrank, 1788) Brumpt, 1927</b></span></p>
<p align="CENTER"><span style="font-size: medium"><b>(Figures 4-27 through 4-32)</b></span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>ETYMOLOGY:</b></span><span style="font-size: medium"><i>Toxo</i></span><span style="font-size: medium"> - arrow + </span><span style="font-size: medium"><i>cara</i></span><span style="font-size: medium"> = head, and </span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> for the domestic cat.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>SYNONYMS:</b></span><span style="font-size: medium"><i>Ascaris cati</i></span><span style="font-size: medium"> Schrank, 1788; </span><span style="font-size: medium"><i>Fusaria mystax</i></span><span style="font-size: medium"> Zeder, 1800; </span><span style="font-size: medium"><i>Ascaris felis,</i></span><span style="font-size: medium"> Gmelin, 1790; </span><span style="font-size: medium"><i>Belascaris </i></span><span style="font-size: medium"><i>mystax</i></span><span style="font-size: medium"> (Zeder, 1800; Leiper, 1907; </span><span style="font-size: medium"><i>Belascaris </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> (Schrank, 1788), Brumpt, 1922; </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>mystax</i></span><span style="font-size: medium"> (Zeder, 1800) Stiles & Brown, 1924.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>HISTORY:</b></span><span style="font-size: medium"> A detailed history of the name </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> is presented by Sprent (1956). Goeze (1782) illustrated a worm from the cat that had large cervical alae. Schrank (1788) gave this worm the name </span><span style="font-size: medium"><i>Ascaris </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">. Zeder (1800) introduced the specific name mystax for this parasite. The name of “</span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">” of Schrank, who referred to the figure of Goeze, therefore has priority. The genus </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium"> was established by Stiles and Hassal (1905) and </span><span style="font-size: medium"><i>Lumbricus </i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium">, the dog ascarid, of Werner (1782), was considered th type species. Leiper (1907) created the genus </span><span style="font-size: medium"><i>Belascaris</i></span><span style="font-size: medium"> with </span><span style="font-size: medium"><i>Ascaris </i></span><span style="font-size: medium"><i>mystax</i></span><span style="font-size: medium"> of Zeder (1800) as the type species, and Leiper differentiated the genus </span><span style="font-size: medium"><i>Belascaris</i></span><span style="font-size: medium"> from other ascarids by the ventriculus located at the base of the esophagus. Stiles and Brown (1924) confirmed that the genus </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium"> had priority over </span><span style="font-size: medium"><i>Belascaris</i></span><span style="font-size: medium">, and they created the name </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>mystax</i></span><span style="font-size: medium"> for the </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium"> species of the cat. However, the name of Schrank has priority over that of Zeder, and, therefore, the common </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium"> of the cat is </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> (Schrank, 1788) Brumpt, 1922.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>GEOGRAPHIC LOCATION:</b></span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> is a cosmopolitan parasite of the domestic cat and probably one of the most commonly encountered parasites. Some prevalences that have been recorded in different countries include: Germany, 45% of 155 cats (Schuster et al., 1997); France, 31% of 129 cats (Petithory et al., 1996); Tasmania, 89% of 39 cats (Milstein and Goldsmid, 1997); Taipei, 42% of 95 cats (Fei and Mo, 1997); Japan, 18.2% (Oikawa et al., 1991); Somalia, 28 % of 50 cats (Gadale et al., 1989): South Africa, 11% of 1,502 cats (Baker et al., 1989). Interestingly a survey of 188 feral cats from the Northern Territory of Australia revealed that only 1% of the cats were infected with </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> (O’Callaghan and Beveridge, 1996). In a careful study of the parasites occurring in litters of kittens in Germany, </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> infections were found in 54 litters of the 70 litters of free-ranging farm cats that were examined (Beelitz et al., 1992). On the other hand, of 30 litters of house cats where both the mothers and kittens had received anthelmintic treatment between weeks 2 through 12 after delivery, only one litter had an infection with </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">. As with many other helminth infections, juvenile cats are more likely to maintain patent infections, as shown in the survey performed in South Africa where the overall prevalence of infection with </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> was 11%, but the prevalence in juvenile cats was 41%. </span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>LOCATION IN HOST:</b></span><span style="font-size: medium"> Adults are found in the small intestine.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>PARASITE IDENTIFICATION:</b></span><span style="font-size: medium"> The adult worms are cream-colored to pinkish and have a length of up to 10 cm (Fig 4-27 and 4-28). Warren (1971) reports males as 3 to 7 cm long and females as 4 to 10 cm long. The adults have distinct cervical alae that are short and wide giving the anterior end the distinct appearance of an arrow. The esophagus is about 2% to 6% of the total body length and terminates in a glandular ventriculus that is about 0.3 to 0.5 mm long. The vulva of the female occurs about 25% to 40% of the body length behind the anterior end. The spicules of the males range from 1.7 to 1.9 mm in length. The egg measures 65 μm by 77 μm and has the pitted eggshell typical of the eggs of this genus of ascaridoids (Fig 4-29). The pits on the eggs of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> are smaller than the pits observed on the eggs of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium">.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>LIFE CYCLE:</b></span><span style="font-size: medium"> The adult worms live in the small intestine and the female produces eggs that are passed in the feces of the cat. The egg is typically passed containing a single cell, and after a period of time in the environment, two molts occur within the eggshell to produce the infective third-stage larva. There has been considerable debate about the number of molts occurring within the eggshell of the ascaridoid parasites, but the majority of evidence seems to be that for certain genera, anyway, that the infective stage is the third-stage larva.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"> Sprent (1956) described the details of the development of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> in the feline host following oral infection with eggs and with mice that had been orally infected with eggs. After having infected kittens with 10,000 embryonated eggs, Sprent found that the larvae were found to migrate away form the alimentary tract before commencing development. By three days after infection, larvae were found in the live and lungs, and there were also larvae present in the stomach wall. Five days after infection, there were larvae in the lungs, tracheal washings, and stomach wall (Fig 4-30 to 4-31). After the tenth day of infection, many larvae were in the lungs and stomach wall, and a number of larvae began to be recovered from the muscle tissues of the cat. The larvae that make the liver-lung migration and return to the stomach wall via the trachea then undergo considerable growth. When kittens were fed mice that had been infected with 10,000 infective eggs of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">, almost all larvae were found to complete their development without undergoing a liver-lung migration, and larvae were only rarely recovered form the muscle tissues of the infected cats. The larva that escapes from the eggshell measures 0.31 mm to 0.42 mm in length. Within the stomach wall of the cat, the larvae grow from 0.4 mm to about 1.3 mm in total length. The molt from third-stage to fourth-stage larvae occurred when the larvae measured 0.999 to 1.235 mm in length, and during this molt there was a marked reorganization of the mouth with the development of the lips characteristic of ascaridoid nematode. The fourth stage larvae were found in the stomach contents, intestinal wall, and intestinal contents. In egg-infected cats, fourth-stage larvae were first observed at 19 days after infection; whereas, in mouse-infected cats, fourth-stage larvae were first observed at 10 days after infection. When the fourth-stage larvae reach a length of about 1.5 mm, it is possible to readily distinguish males from females on the morphology of the genital rudiment, and as growth progressed the spicules of the males become evident and the tails of the males were broader than the tails of the female larvae. The molt from the fourth to the fifth larval or young adult stage occurred within the intestinal lumen when the larvae were 4.3 to 6.5 mm in length. The fourth-stage larvae could be distinguished from the young adults of similar length by the much thinner cuticular annulations on the adults. The smallest female observed by Sprent to have eggs in its uterus was 55 mm long. Eggs were first observed in the feces beginning 56 days after the infection of the cats. Dr. Stoye (personal correspondence with Dr. J.C. Parsons) has reported that in four older cats which were each experimentally infected with 500 embryonated eggs, the observed prepatent peiod was 38, 39, 39, and 40 days.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"> Sprent (1956) looked for the possibility of transplacental transmission from the queen to the developing kittens. During the last 4 weeks of gestation, a pregnant queen was given three inocula of 10,000 embryonated eggs. Larvae were not recovered from the tissues of the kittens examined 3 or 4 days after birth. </span></p>
<p align="JUSTIFY"><span style="font-size: medium"> Swerczek et al. (1971) showed that transmammary transmission commonly occurs with </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">. The examination at birth of 78 kittens from 20 queens that were naturally infected with </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium"> and 14 kittens from 7 queens that were experimentally infected with 300 to 2,000 eggs of </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium"> per day from day 2 to 56 prepartum revealed no larvae in the organs of the kittens when they were examined. When 12 kittens were examined 15 to 22 days after natural delivery from 5 queens that had been orally infected with 2,000 eggs of </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium"> for 1 to 10 days prepartum, a total of 7,959 larvae were recovered, with most of the larvae being recovered from the gastrointestinal tract. Larvae were not found in the 5 littermates (one from each litter) that has not been allowed to nurse. These authors also found larvae in the mammary glands and milk of these 5 queens. The authors went on to show that 19 kittens that were derived by caesarean section from 6 queens and raised colostrum-free to maturity remained free of infections with </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"> Paratenic hosts are probably routinely involved in the life cycle of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">. The larvae are capable of persisting in the tissues of cockroaches (Sprent, 1956), earthworms (Okoshi and Usui, 1968); mice (Schön and Stoye, 1986), chickens (Okoshi and Usui, 1968, Sprent, 1956), dogs (Sprent, 1956), and lambs (Sprent, 1956). Beaver et al. (1952) showed that both </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> and </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium"> produced lesions in white mice that were similar to those observed in human cases of visceral larva migrans (Fig 4-32). Fülleborn (1921), Hoeppli et al., 1949, and Sprent (1952) showed that the larvae undergo a liver-lung migration in the mouse before they settled down in the musculature or brain. Sprent (1956) found that the larvae of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> mainly are found in the somatic musculature. Nichols (1956) described the morphology of the larva of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> and differentiated it from the larva of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium">, the major difference in the two worms was the diameter of the body which is narrower in Toxocara cati (</span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> larvae have a width that is never greater than 18 </span><span style="font-family: 'WP MathA'"><span style="font-size: medium"></span></span><span style="font-size: medium">m, while the larvae of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium"> are typically 18 </span><span style="font-family: 'WP MathA'"><span style="font-size: medium"></span></span><span style="font-size: medium">m wide or wider.)</span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>CLINICAL PRESENTATION AND PATHOGENESIS:</b></span><span style="font-size: medium"> Kittens infected with </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> often show no clinical signs due to the infection. However, it is generally considered that kittens are capable of displaying signs similar to puppies with moderate worm burdens, i.e., a pot-bellied appearance and a general failure to thrive. On occasion it may be possible to palpate thickened intestines. </span></p>
<p align="JUSTIFY"><span style="font-size: medium"> Aoki et al. (1990) reported on a 7-year-old domestic male cat that had anorexia, vomiting, and an enlarged abdomen. A laparotomy revealed an adult </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> in the abdominal cavity and a gastric ulcer that had perforated the stomach wall. The next day, acute perforations of the stomach again occurred, and during a second surgery, the two new gastric perforations were repaired and four adult </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium"><i> cati</i></span><span style="font-size: medium"> were removed from the abdominal cavity. Unfortunately, the cat died during recovery from the second emergency surgery. It is difficult to determine whether the ascaridoids were the cause of the gastric perforation or were simply migrating into lesions caused by some other underlying cause.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"> Swerczek (1969) and Swerczek et al. (1970) in studies on the comparative development of medial hypertrophy of the pulmonary arteries in cats with various helminth infections, described the hematological changes in experimentally infected cats. He reported that eosinophils may increase to up to 35% of the total leukocytes. Also, he found that anemia was typically not associated with the infection. Swerczek concluded that “</span><span style="font-size: medium"><i>T. cati</i></span><span style="font-size: medium"> migration produces severe lesions and is probably the most common cause of MHPA [medial hypertrophy of the pulmonary vessels] in cats.” This was observed in cats that had received doses of eggs of a period of several weeks; cats that received a single inoculum had less severe lesions that were similar to those of cats receiving weekly inocula. After a single inoculum, the lungs of cats would appear to have slight lesions 10 weeks after infection and would appear normal 14 weeks after infection. The histopathological lesions of MHPA can be quite remarkable with media of the arteries becoming very enlarged. Potential causes of the observed hypertrophy of the media of the vessels are allergy with histamine release (Weatherly and Hamilton, 1984) or pulmonary hypertension (Mecham et al. 1987).</span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>TREATMENT:</b></span><span style="font-size: medium"> Treatment of gastrointestinal infections with </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> is relatively straightforward. Approved compounds include piperazine, pyrantal, dichlorvos, febantel formulated with praziquantel, selamectin, milbemycin oxime, moxidectin, emodepside formulated with praziquantel and pyrantel formulated with praziquantel. Ridley et al. (1991) reported on the use of pyrantel pamoate for the treatment of </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium"> in kittens experimentally infected by the feeding of infected mice; at 20 mg of base per kg body weight, this compound was 100% effective in removing the worms from these cats. The febantel formulated with praziquantel has been shown to be 100% effective in removing <em>Toxocara cati</em> from cats (Corwin et al., 1984). Ivermectin (200 </span><span style="font-family: 'WP MathA'"><span style="font-size: medium"></span></span><span style="font-size: medium">g per kilogram body weight) has been found to remove adult </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> from infected cats (Kirkpatrick and Megella, 1987). Milbemycin oxime (500 </span><span style="font-family: 'WP MathA'"><span style="font-size: medium"></span></span><span style="font-size: medium">g per kilogram body weight) is also effective against the adults of </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">. </span></p>
<p align="JUSTIFY"><span style="font-size: medium">Pharmacological prevention of the transmammary transmission of larvae has been shown using a topical formulation containing emodepside and praziquantel (Böhm, et al., 2015). When this formulation was placed on the pregnant queen at day 60 of pregnancy, vertical transmission of <i>Toxocara cati</i> was reduced 98.7% compared to controls. </span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>EPIZOOTIOLOGY:</b></span><span style="font-size: medium"> Cats can be infected by one of three routes, by the ingestion of infective eggs, by the ingestion of a mouse containing larvae, or by the transmammary infection of kittens. Dubinsky et al. (1995) showed that small mammals were probably a major means by which the infection is maintained in cats that are allowed to hunt in Slovakia. Webster and Macdonald (1995) examined a total of 510 brown rats from 11 rural farms in the United Kingdom, and they found that 15% of the rats were infected with the larvae of <em>Toxocara cati</em>. Sprent (1956) infected chickens and recovered 10 larvae from only one of the four chicks that were given 5,000 eggs. Okoshi and Usui (1968) successfully infected a number of chickens by feeding them the eggs of <em>Toxocara cati</em> and verified that the larvae were present in the tissues of the chickens for at least three months after infection. However, there has been very little effort to determine the role of birds in the transmission of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> to cats. Sprent did recover larvae from earthworms that were fed embryonated eggs. Takahashi et al. (1990) showed that cockroaches that ingest the eggs of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium"> were capable of excreting the eggs in their feces over a two day period and that these eggs were still infectious; they went on to postulate that such insects can serve as vectors as they carry the eggs from fecal contaminated areas to food stuffs. It is unclear how often cats are infected by the ingestion of infective eggs. Uga et al (1996) examined the defecation habits of cats around three sand lots in public parks in Nishinomiya City, Japan, through the use of video-recordings. Around 4 to 24 cats visited each of the sand lots. Cats were observed to defecate in the three sand lots a total of 961 times in about 4 ½ months while dogs were only observed to defecate in these areas 11 times. One of the three sand lots was highly contaminated with the eggs of </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium">, and 8 of the 12 cats that visited this site were observed to be infected with </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">. However, although cats are routinely visiting these sites there is no information on whether they are becoming infected from this type of source. In a survey of 181 cats for </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium"> in Dublin (O’Lorcain, 1994), no cats less than 4 weeks old were found to be infected, the highest prevalence of infection was found in cats between 12 to 24 weeks of age, and there was no apparent difference in the prevalence of infection between male and female cats. The work of Beelitz et al. (1992) would suggest that, as expected, the levels of transmission are greatest between free-ranging cats and lowest when cats receive adequate veterinary care.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>HAZARDS TO OTHER ANIMALS:</b></span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium"> will infect small mammals but their is little information on the effects on these hosts. The experimental infection of mice with the eggs of </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">, unlike those of </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium">, seldom result in ocular lesions in the infected mice (Olson and Petteway, 1971). Prociv (1986) showed that in guinea pigs the larvae of </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium"> tend to remain in the musculature rather than moving into the nervous system as do the larvae of </span><span style="font-size: medium"><i>Toxocara canis</i></span><span style="font-size: medium">. </span></p>
<p align="JUSTIFY"><span style="font-size: medium"> Roneus (1963 and 1966) presented rather convincing evidence that the larvae of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> were capable of being a cause of “white-spot” disease in the liver of pigs. He showed that following infections with </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">, </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium">, </span><span style="font-size: medium"><i>Parascaris </i></span><span style="font-size: medium"><i>equorum</i></span><span style="font-size: medium">, or </span><span style="font-size: medium"><i>Ascaris </i></span><span style="font-size: medium"><i>suum</i></span><span style="font-size: medium"> that white spots appears on the surface and deep in the livers of infected pigs between a few days and up to two months after infection. Thus, although the disease induced in swine may not be great, there is the potential for economic loss due to this parasite if pigs are infected.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>HAZARD TO HUMANS:</b></span><span style="font-size: medium"> There have been reports of humans who have passed the adult stage of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">. To quote from Dr. Paul C. Beaver (Beaver et al., 1984) "Intestinal infections with adult-stage </span><span style="font-size: medium"><i>T. canis</i></span><span style="font-size: medium"> and </span><span style="font-size: medium"><i>T. cati</i></span><span style="font-size: medium"> have been reported in humans, but such records are generally unreliable. In the few cases in which an adult worm was unquestionably passed from the anus or mouth of a child, circumstances have suggested that the worm had been ingested as a mature or, more likely, an immature adult, having been taken form the feces or vomitus of an infected dog or cat (von Reyn et al., 1978)."</span></p>
<p align="JUSTIFY"><span style="font-size: medium"> It is believed that most cases of human larval toxocariasis (visceral larva migrans) are due to the larvae of </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium"><i> canis</i></span><span style="font-size: medium">. In histological sections, the larvae of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> are slightly smaller, have a diameter of 15 to 16 μm, than the larvae of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium"> which have a diameter or 18 </span><span style="font-family: 'WP MathA'"><span style="font-size: medium"></span></span><span style="font-size: medium">m or greater. Thus, when biopsies are performed it is often possible to identify the larvae that are observed as the larvae of </span><span style="font-size: medium"><i>Toxocara canis</i></span><span style="font-size: medium">. There have been two cases where the larvae of </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> have been identified in the tissues of humans. Karpinski et al (1956) report on two cases of human larval toxocariasis, and in a two-year-old boy from Philadelphia, they found small larvae in a liver biopsy that they thought were </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> due to their small size and the boy being in contact with an infected kitten and without any known canine contact. In a second case, Schoenfeld et al., 1964 found numerous larvae that were identified as </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> in the brain tissue of a five-year-old girl who died after entering a hospital in Israel, comatose with fever and convulsions. Nogakura et al. (1990) reported on a serological procedure for differentiating </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>canis</i></span><span style="font-size: medium"> and </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium"> in a gel diffusion method and examined sera from 17 cases of suspected toxocariasis. Virginia et al. (1991) examined the sera of 54 children from Recife City, Brazil who had signs of, tropical eosinophilia syndrome. They found 21 sera that were positive for antibodies to </span><span style="font-size: medium"><i>Toxocara</i></span><span style="font-size: medium">, and after further analysis of sera from six of these children, they identified one that was felt to be due to </span><span style="font-size: medium"><i>Toxocara </i></span><span style="font-size: medium"><i>cati</i></span><span style="font-size: medium">. </span></p>
<p align="JUSTIFY"><span style="font-size: medium"><b>CONTROL/PREVENTION:</b></span><span style="font-size: medium"> The control of </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium"> in the cat still depends on the diagnosis of infection and treatment of cats shedding eggs. The monthly preventative approved for cats, ivermectin at 24 μg/kg, does not significantly reduce the number of adult </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">; Blagburn et al. (1987) showed that a dose of 300 μg/kg of ivermectin administered subcutaneously was required for the removal of adult </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">. However, monthly preventatives containing milbemycin, selamectin or moxidectin are effective at killing <em>Toxocara cati</em>. However, it is still prudent to prevent cats from obtaining infections by the ingestion of infective eggs or mammalian paratenic hosts.</span></p>
<p align="JUSTIFY"><span style="font-size: medium"> Transmammary transmission should be presumed to occur, and kittens should be considered as infected and treated every 3 weeks, beginning at 3 weeks of age, until they are old enough to be given one of the approved preventatives on a monthly basis for the rest of their lives. </span></p>
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<p align="JUSTIFY"><span style="font-size: medium">Figure 4-27</span><span style="font-size: medium"><i>. Toxocara cati</i></span><span style="font-size: medium">. Adult worms on the mucosa of the small intestine of a naturally infected cat.</span></p>
<p align="JUSTIFY"><span style="font-size: medium">Figure 4-28. </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">. Adult male and female worms, formalin fixed. Notice that the female tail is straight while both the head and the tail of the male are curled.</span></p>
<p align="JUSTIFY"><span style="font-size: medium">Figure 4-29. </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">. Egg passed in the feces of an infected cat with the thick shell that has a dimpled surface.</span></p>
<p align="JUSTIFY"><span style="font-size: medium">Figure 4-30. </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">. This histologic section is through a larva that was discovered as an incidental finding in a cat at necropsy.</span></p>
<p align="JUSTIFY"><span style="font-size: medium">Figure 4-31. </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">. Larva teased by Dr. M. Georgi from the heart tissue of the cat described above.</span></p>
<p align="JUSTIFY"><span style="font-size: medium">Figure 4-32. </span><span style="font-size: medium"><i>Toxocara cati</i></span><span style="font-size: medium">. Section through the liver of a mouse that has been experimentally infected with Toxocara cati by the feeding of eggs containing infective larvae. Note the large lateral cords characteristic of these larvae in tissue sections.</span></p> |
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