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Abstract

Effect of Trypanosoma congolense on the haematology and reproductive function of Baoulé bulls.

Abstract

A herd of 53 Baoulé bulls, considered to be trypanoresistant, was used to assess the effects of natural infection with Trypanosoma congolense on the blood formula and testicular function. Parasitological examination of blood showed that 8 of the bulls were infected with T. congolense. Haematological values for the non-infected animals were 35.5 ± 4.0% for haematocrit, 63.5 ± 16.1% for lymphocytes, 4.6 ± 5.3% for monocytes, 24.5 ± 13.6% for the segmented neutrophilic polymorphonuclear cells, 1.2 ± 2.0% for the non-segmented neutrophilic polymorphonuclear cells, and 6.1 ± 6.4% for eosinophils; no basophils were seen. Trypanosome infection did not cause any significant differences (P<0.05) in these values, except for haematocrit (28.0 ± 9.4%), confirming the trypanoresistance of this breed. The mean daily quantity of spermatozoa produced by the non-infected control animals was 382 ± 334 × 106. The epididymis head contained 0.6 ± 1 × 109 spermatozoa, the corpus 0.3 ± 0.3 × 109 and the cauda 1.2 ± 1.8 × 109. Average values for infected bulls tended to be about 30% lower, but there was great individual variation. Morphometric analysis of the testicle indicated that during trypanosome infection, there is a significant reduction (31.8%, P<0.05, in the total volume of the Leydig cells: 4.4 ± 0.9 cm3 for the controls (n = 5) and 3.0 ± 0.8 cm3 for the infected animals (n = 8)). The daily production of round spermatids (DRSP) expressed/testicle or /Sertoli cell were significantly reduced (P<0.05) and were, respectively, for control and infected animals, 6.1 ± 2.0 and 3.1 ± 1.9 × 108 for the DRSP and 5.2 ± 0.7 and 2.8 ± 2 round spermatids for the Sertoli cells. It is concluded that the trypanosome infection alters both the interstitial tissue and the meiotic division of the germinal cells, which leads to a lower daily round spermatid production/g of testis.