Population dynamics of Toxocara canis in pigs receiving a single or multiple infection

Abstract

The population dynamics of Toxocara canis in pigs, and their immune response to a primary and a challenge infection, were studied by parasitological, haematological and serological parameters. Seventy pigs were divided into 4 groups; 35 pigs received a primary infection (group A), 15 pigs received both a primary and a challenge infection (group B), 15 pigs received the challenge infection only (group C), and 5 pigs served as helminth-free controls (group NC). A dose of 50,000 eggs was administered for the primary infection (day 0) and a dose of 10,000 eggs was given for the challenge infection (day 28). On days 7, 14, 21 and 28 p.i., 5 pigs of group A, and on days 35, 42 and 49 p.i., 5 pigs from each of groups A, B and C were necropsied. Numbers of recovered larvae varied widely among the 5 pigs of each group on all days of necropsy. Toxocara canis larvae were recovered predominantly from the lungs; migration of larvae to other organs or tissues from the lungs was restricted. In group A, the larval burden in the lungs peaked on day 14 p.i., and the larval densities decreased significantly over time. Thereafter, the majority of larvae were recovered from the lungs until the end of the experiment (day 49 p.i.). A few larvae were found in the muscles and brain until day 42 p.i., and 2 larvae were found in the eyes of 2 pigs on day 35 p.i. There was little evidence of protective immunity to a challenge infection in this experiment. The eosinophil levels tended not to increase in pigs receiving a challenge infection, in contrast to the challenge control pigs. The fact that T. canis larvae migrate and persist in the tissues of pigs for more than 1 month suggests a zoonotic risk in infected pigs. The relevance of these data to the population biology and immunology of porcine and human toxocarosis is discussed.

EXPERIMENTAL INFECTION WITH Toxocara cati IN PIGS: MIGRATORY PATTERN AND PATHOLOGICAL RESPONSE IN EARLY PHASE

“…Our results also agree with previous observations of macroscopic lesions in pigs inoculated with T. canis 4,10,17,20 . White spots on the liver were also observed by TAIRA et al 24 . One notable difference between our study and previous research that inoculated T. canis , was the absence of the typical granulomatous reaction in our sample.…”

“…In pigs, DONE et al 4 reported that T. canis larvae have been previously shown to migrate primarily to the liver and lungs; HELWIGH et al 10 and TAIRA et al 24 , to the lungs and lymph nodes; SOMMERFELT et at. 20 observed to the lymph nodes, liver, and lungs.…”

“…The results of multiple studies vary based on the animal model chosen, the parasite species inoculated, and the larval dose(s) used for infection. Experimental infections with T. canis and T. cati have been described in different animal models, including mice, Mongolian gerbils, rats, and chickens 2,3,5,8,11,12,15,18,22,24,25 .…”

“…Pigs have been used as an animal model for the study of the Toxocariasis due to T. canis . Pigs experimentally infected with T. canis were previously used to study the migratory pattern of the parasite as well as to analyze the pathological changes, immunological response, and hematological disturbances triggered by infection 3,9,15,19,20,24 . T. canis is better recognized as the main cause of the toxocariasis.…”

Toxocara cati larva migrans in domestic pigs - detected at slaughterhouse control in Norway

“…Experimental infections with Toxocara canis have shown that pigs are suitable hosts and that larva migrans can occur with the liver and lungs being favoured sites for the larvae during early infection stages [2,3]. To the best of our knowledge there are no published cases of naturally infected pigs with Toxocara cati larva migrans, although pigs are listed as a suitable paratenic host [4] and T. cati eggs have been detected in the faeces of fattening pigs [5].…”