Toxocara canis
(Figures 4-33 through 4-35)
In 1988, Parsons et al. described a case of disseminated granulomatous disease in a cat that was caused by the larvae of the dog roundworm, Toxocaracanis (Fig. 4-33). The larvae were identified on the basis morphology, being greater in diameter than the 17 m of the larvae of Toxocaracati whien they appear in tissues. This cat had been housed for 19 days in the research facilities of the School of Veterinary Medicine in Madison, WI, and had been considered normal except for being noted as pyrexiuc throughout the 19-day period. At necrospy, the cat was found to have well delineated, raised g, grey-to-white nodules that were up to 4 mm in diameter within the cortical parenchyma of the kidneys and within the epicardium and myocardium of both ventricles (Fig 4-34). Lesions were also noted on the liver, lungs, spleen, diaphragm, and intestinal serosa. Upon histologic examination, the nodules were found to be large eosinophilic granulomas that contained a larva of Toxocaracanis. In the lungs, medial hypertrophy of the pulmonary vessels was noted along with severe eosinophilic endarteritis (Fig 4-35). Similar lesions have been noted in cats experimentally infected with Toxocaracanis (Bhowmick, 1964; Parsons, 1989; Swerczek, 1969). In experimentally infected cats, peak eosinophil counts occurred at 25 to 39 days after infection, and challenge infections prolonged the period of increased eosinophilia. In some cats, eosinophils were noted to be up to 50% of the circulating white-blood cells.
Lee et al. (1993) reported that the necropsy of 55 cats around Kuala Lumpur, Malaysia, revealed that 15 of these cats were infected with adults of the genus Toxocara. They stated that 12 of the cats were infected with Toxocaracati, 3 were infected with Toxocaracanis, and that 3 had mixed infections of Toxocaracati and Toxocaracanis.
REFERENCES:
Bhowmick DK. 1964. Deiträge zu dem problem der wanderweg der askaridenlarven (Ascaris
lumbricoiudes Linné 1758 und Toxocara canis Wener 1782) im experimentellen und natüralichen Wirt.. Zeitschrift für Parasitenkunde 24:121-168.
Lee CC, Cheng NY, Bohari Y. 1993. Toxocara canis from domestic cats in Kuala Lumpur. Trop Biomed 10:79-80.
Parsons JC, Bowman DD, Grieve RB. 1988. Disseminated granulomatous disease in a cat caused by larvae of Toxocara canis. J Comp Path 99:343-346.
Parsons JC, Bowman DD, Grieve RB. 1989. Pathological and haematological responses of cats experimentally infected with Toxocara canis larvae. Int J Parasitol 19:479-488.
Swerczek TW. 1969. Medial hyperplasia of the pulmonary arteries of cats. University Microfilms International, Ann Arbor, MI. 199 pp.
Figure 4-33. Toxocara canis. Embryonated egg containing a third-stage infective larva.
Figure 4-34. Toxocara canis. Kidney of an infected cat showing the large eosinophilic granulomas that develop around the larvae of the canine species in this host.
Figure 4-35. Toxocara canis. Medial hypertrophy of the pulmonary vessels of a specific-pathogen-free cat necropsied 39 days after being experimentally infected with this canine ascarid. Note the highly thickened medial layer of the pulmonary vessel.