Experimental Toxocara canis infection in chickens

Abstract

The objective of this study was to determine the development phases of Toxocara canis eggs outside the host and the migration of larvae in the internal organs of chickens infected by ingestion of embryonated T. canis eggs. Under a microscope observation of T. canis eggs which were incubated in a petri dish containing 5 mL of distilled water at 30 – 33◦C with regularly aerated, this study showed the development of T. canis egg through various stages, including one cell, two cells, three cells, four cells, early morula, late morula, blastula, gastrula, tadpole, pre-larva, embryonated larva. In addition, it took approximately 9 days for T. canis eggs to hatch and for infective larvae to develop at 30 - 33◦C. A total of 50 chickens were randomly assigned to 3 groups including group I (10 chicks/group) was served as control group without T. canis eggs inoculation; two treatment groups II and III (20 chicks/group) were orally inoculated with 500 or 1000 T. canis eggs, respectively. On 1, 3, 6, 15 and 30 days post inoculation (dpi), two chickens/control group and 4 chickens/treatment group were necropsied. The results showed that the percentage of larvae recovered varied from 14.00 to 33.93% and 13.07 to 32.00% in treatment groups II and III, respectively. After 1, 3, 6, and 30 dpi, the significant differences about the number of larvae recovered in two treatment groups were found (P < 0.05). In both treatment groups, the percentage of larvae recovered from livers was higher than that in lung tissue. For 6 dpi, small white foci on the liver’s surface were seen. Interstitial pneumonia, petechial hemorrhages, dark or gray inflammatory nodules in the lung tissue and the atelectatic area were observed. Histopathology examination revealed infiltrations of leukocytes and eosinophil scattered in the liver and lung tissue.