Sarwar Khan, M

Epidemiology And Economic Losses Of Trichostrongylid Parasites In Sheep - 1997

The meteorological data recorded during the study period from 1.1.96 to 31.12.96 showed the maximum temperature in June as
36.5°C and minimum temperature in December as 6.8°C. Maximum and minimum Humidity was recorded in the month of September and April as 85% and 55% respectively. The maximum rainfall during the year was recorded in the month of August as 660 mm.
The faecal egg counts of sheep grazing on permanent pasture showed the minimum EPG during first week of January while maximum EPG on nid of September and first week of October.
Pasture larval counts were performed on permanent pasture and experimental plot for the recovery of trichostrongylid larvae. The maximum number of larvae was recovered on 16th September, 1996, while minimum number was recovered in January and February from permanent pasture and experimental plot respectively. Two species of trichostrongylids were identified i.e. Haemonchus contortus and Trichostrongvlus colubriformis.
The faecal and larval counts were very low in the months of January and February, the counts started rising in March. Peak counts were seen in the month of September. Decline in counts started in late October and reached to minimum in December.
Mature and immature worm counts of slaughtered sheep were performed at 15 days interval. The, overall prevalence oftrichostrongylid parasites was 34%. The maximum number of mature parasites were seen during first week of October which was886 whereas maximum number of immature parasites including hypobiotic was 326 on 1st of December. During this study the average fecundity/female of contortus and L colubriformis parasites were calculated as 721 and 209 respectively. A spring rise in worm egg counts was experienced in mid of March. A pen parturient rise in the worm egg counts of pregnant and lactating ewes indicated the maximum counts during lambing week.
An experimental group of sheep with mixed infection of trichostrongylid parasites showed the similar pattern of EPG counts as of naturally infected sheep.
A study was performed to evaluate any protection provided by a particular Flaemoglobin type to trichostrongylid infection hut not difference could be observed. The Asparate Aminotransferase (AST) and total protein levels of infected sheep were decreased as a result of increase in the intensity of infection.
A decrease in R.B.C. counts, Haemoglobin, Packed cell volume and lymphocyte counts was observed both in experimentally and naturally infected slaughtered sheep. However, an increase in total leukocytic count (TLC) alongwith an increase in the ratio of neutrophils, eosinophils and basophils was observed.
At the end of experiment infected sheep gained 5.71 Kg/head less body weight and produced 4 3 grn less wool as compared with non-infected group. Based on epidemiological information the suggestions for control of the, trichostrongylid infection are submitted alongwi th recommendations for further studies.

Department of Clinical Medicine & Surgery
Phd. Thesis


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