Manuel Gutiérrez Quiroz

Prevalence of anti-T canis antibodies in stray dogs in Mexico City

UNLABELLED Toxocara canis is a common intestinal helminth found in dogs. In humans, it is a cause of Visceral Larva Migrans (VLM), a zoonosis rarely studied in Mexico. The aim of this study is to examine, by means of the indirect haemaglutination test (IHAT), the prevalence of antibodies of T. canis in the serum of stray dogs in Mexico City. METHODS AND MATERIALS 141 stray dog serum samples from three different districts of the city were analyzed: Iztacalco (49), Iztapalapa (49) and Coyoacan (43). In each location three study groups were formed. Group I with 35 dogs (less than a year old), Group II with 91 dogs (ages 1<or=n<6) and Group III with 15 dogs (ages 6 and over). An extract of raw adult T. canis worms was used as an antigen. Finally, a modified version of Boydens IHA serological test was carried out. RESULTS Out of the 141 sera, 94 (40 males and 54 females) proved positive (dilution titres of from 1:32 to 1:4096) with a global infection prevalence of 66.7%. The frequency of infected dogs in Iztacalco was 61.2%, 51% in Iztapalapa and 90.7% in Coyoacan. The largest seroreactivity was found in Group II (ages 1-6) with 61 positive tests and a total frequency of 43.3%. CONCLUSIONS The high seroprevalence of anti-T. canis antibodies found in the dogs of the study population is an indicator of the contact which exists between these animals and the parasite. This is the result of the high degree of contamination of the soil of Mexico City with the parasites eggs. Paradoxically, Coyoacan, with more green areas, is also the most polluted municipality. Statistical analysis confirms this. Dogs seek green areas to defecate. There exists a serious risk for the population of being infected with Visceral larva migrans.

Estudio de la respuesta inmune humoral en cerdos infectados con huevos y posoncosferas de Taeina solium

Due to the importance of cysticercosis in Mexico and Latin America and to the fact that in the last years another mechanism of infection for this disease has been proposed, i.e. through postoncospheres and immunosuppression of the host, we have considered relevant to perform the present work, which consisted in assessing the immune response induced by dexamethasone as well as that produced by parasites in pigs infected with T. solium eggs, or postoncosphere-infected, and in postoncosphere-infected and dexamethasone-treated animals. We used 10 recently weaned pigs, three were used as controls, two of them without the drug and one with it; two were infected with T. solium eggs; five with postoncospheres receiving also dexamethasone three of them.We evaluated the humoral response against parasite antigen using indirect haemagglutination (IH) and ELISA methods Results of the immune humoral response revealed titres of up to 1:128 in T. solium eggs infected animals, of 1:16 in postoncosphere infected animals, and of 1:32 towards the end of the experiment in postoncosphere plus dexamethasone animals. Absorbance titres with ELISA confirmed these findings. Data obtained by IH show that the antibody titres of the pigs challenged with postoncospheres and postoncospheres plus dexamethasone are positive as compared to the titres obtained in the pigs infected with T. solium eggs. Results from the ELISA confirmed this finding, since, from weeks 14 to 17, the pigs became positive, behaving as those pigs that developed cysticercosis. This is relevant as it indicates that the antiposcosphere antibodies recognized antigens of T. solium larvae.