Objective.

The aim of the present study is to report for the first time the natural infection of a sheep with Nematodirus filicollis in the sub-humid tropics of Mexico.

Materials and methods.

Faecal samples were processed to identify and quantify faecal nematode eggs per gram of feces (EPG) using the flotation and modified McMaster techniques. Also, faecal cultures were made using the Corticelli-Lai technique.

Results.

The ewe showed a mixed infection with Trichuris spp. (100 EPG), Nematodirus (100 EPG) and other strongylida nematodes (1500 EPG). The egg size of Nematodirus spp. was 202±3 µ long and 97±2 µ wide. Larvae of Haemonchus, Trichostrongylus, Oesophagostomum and Nematodirus genera were identified from de faecal cultures. Nematodirus larvae averaged 955±8.0 µ long and 28±0.5 µ wide. Whereas, the average length of the sheath tail was 233.4±41.6 µ.

Conclusions.

According to the morphological traits of eggs and larvae, it is concluded that the infection of the sheep corresponded to Nematodirus filicollis. It is concluded that N. filicollis is able to survive in the sub-humid tropics of Mexico and for the first time an acquired natural infection of this nematode in a sheep is reported.

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