COMPARATIVE STUDY OF TRYPANOSOMOSIS EXPERIMENTALLY INDUCED IN SAVANNAH BROWN GOATS USING Trypanosoma brucei, Trypanosoma congolense AND Trypanosoma vivax.

COMPARATIVE STUDY OF TRYPANOSOMOSIS EXPERIMENTALLY INDUCED IN SAVANNAH BROWN GOATS USING Trypanosoma brucei, Trypanosoma congolense AND Trypanosoma vivax.

Abstract:

Trypanosomosis in the Savannah Brown (SB) breed of goat was evaluated in a two phase investigation. The first phase involved the study oi the prevalence of natural trypanosomosis in the SB goat in its natural habitat of the Guinea and Sudan Savannah zones of Northern Nigeria. The study which spanned 28 months involved the random examination of 717 goats of all sexes and aged between 3 months and 5 years and from a total of 42 flocks through physical and haematological evaluations. These goats were kept by nomadic Fulani cattle herdsmen; established private livestock farms; Institutional Livestock farms and household flocks, which were receiving Veterinary Health Services regularly or on request. Twenty of the goats were positive for trypanosome parasites, giving an infection rate of 2.79%. Out of 20 goats sampled in the Southern Guinea Savannah 2 (infection rate of 10.00%) were positive, 11 out of 522 goats (2.1096) in the Northern Guinea Savannah and 7 out of 175 goats (4.00%) in the Sudan Savannah were also positive. Major clinical signs observed included orchitis, pyrexia of up to 41.0°C, abortion, emaciation in those positive for trypanosome parasites and weak kids born to infected does. T. vivax was the only trypanosome species isolated. The only potential trypanosome vectors identified were biting flies namely Stomaxys calcitrans, Tabanus sp., Hipobosca sp. and Musca spp. The study revealed the occurrence of natural trypanosomosis in the Savannah Brown goat in its presumed tsetse-fly free Savannah zone where this breeed of goat is predominantly found: T. vivax was the only trypanosome from this zone, a finding which confirm the observation of earlier workers that T. vivax is easily transmitted by biting flies. The result goes forth to show the need for vigorous control measures against trypanosomosis in the small ruminants represented by this breed of goat in an effort to enhance the regular supply of animal protein to the teeming population as this breed of goat is a major source of meat in Nigeria. A comparative study of trypanosomosis experimentally induced in the Savannah Brown breed of goats by using T. brucei, T. congolense and T. vivax was carried out, using four groups of 8 Savannah Brown bucks each, aged between 6-12 months. An aspect of it involved observing clinical and haematologicai manifestations of trypanosomosis due to these three pathogenic African animal irypanosomes. One group was inoculated via the jugular route with T. vivax (stabilate 146), another with T. cungoleme (stabilate 136), the third group with T. brucei (stabilate 135) and the fourth group used as uninfected control. The goats were later bled at regular intervals and level of parasitaemia, rbc and pcv levels, total wbc levels, total protein and body- weights evaluated using approved standard procedures at regular intervals. Prcpatcnt periods observed were 2.3, 4.3 and 4.4 days for the T. vivax, T. brucei and T. congoleme infected groups respectively. Observed clinical signs included fluctuating pyrexia which in most cases coincided with parasitaemia. Parasitaemic peaks were pronounced in the T. brucei group, an indication that this trypanosome species is pathogenic to goats contrary to previous reports. The lowest mean pcv level of 8.0% occured in the T. congolcnsc group. The greatest fall in mean rbc level was in the T. vivax group whilst the least fall was in the T. brucei group. The disease produced three distinct phases namely the acute ( 0 – 1 5 days post infection), subacute (16 – 33 days) and chronic (34 – 74 days). Anaemia was of the normocytic normochromic form in the early stages of the disease but became microcytic normochromic at the latter stage in all the infected groups. The primary leucocyte response in all the infected groups was lymphocytosis and later neutrophilia in the T. vivax group, concurrent lymphocytosis and neutrophilia in the T. congolense and T. brucei groups, though there occurred neutropenia in the T. hrucei group in the chronic phase. Bilateral epiphora was very severe in the T. vivax and T. congolense infected goats. The occular discharges of some of the infected goats were found to he positive for trypanosome parasites especially during period of peak parasitaemia. How the parasite got in to the occular discharges cannot be explained from our study. Central nervous system complications like trembling, paddling movements, limb paralysis, staggering were observed most particularly in the T. brucei-infected goats. All the infected groups had progressive fall in mean body weights especially in the chronic phase of the infection. Most of the observations here agree with findings reported for trypanosome infected cattle, thus further indicating that the Savannah Brown goal is highly susceptible to Uypanosomosis in the same vein as it s cattle counterpart. Also that this breed of goat is highly susceptible to all the three species of trypanosomes contrary to earlier reports that T. brucei was as pathogenic to small ruminants as T. vivax and T. congolense arc. The pathological changes due to experimentally induced trypanomosis due T. brucei, T. congolense and T. vivax were also investigated. Carcasses of all infected goats were anaemic especially in the subacute and chronic cases. Lymphoid organs (lymph nodes and spleen) were enlarged and hyperplastic, livers of infected goats were enlargement with areas of necrosis as well as fibrous connective tissue proliferation especially in the T. brucei and T. congolense infected goats. In the T brucei and T. congolense infected goats, kidney lesions included areas of petechial and echymotic haemorrhages in the cortex and medulla regions as well as areas of focal and diffuse necrosis in the proximal and distal convoluted tubules. Haemorrhages of tracheal and bronchial mucosal surfaces as well as mononuclear cellular infilteration of the alveoli were evident in the T. brucei and T. congolense infected goats. All except one of the goats that developed cough were negative for bacterial isolates. Testicles were atrophied; they had also undergone degeneration as shown by the distortated basal layers. Also seminiferous tubules necrosis, fibrous tissue proliferative and aspermia in the chronic stages in all the infected goats. Pericardial space fluid ranged from 20 – 45 mis compared to 5 – 10 mis in the control group. The T. brucei and T. congolense-infected goats manifested areas of necrosis as well as infilteration of mononuclear cells in the myocardia. Although brain and pituitary gland capillaries were highly congested but had no significant microscopic lesions were observed in all the infected goats. Impression smears taken at post mortem from jugular and aortic blood vessels were positive for trypanosomes though at very low parasitaemia. However smears from organs at post mortem were negative for trypanosome in all the infected goats. The three trypanosome species produced severe lesions which were closely related. These lesions so produced could adversely affect the performance of the goats affected goats. The effect of trypanosomosis on the serum biochemical components was studied during this second phase. The experimental goats were bled at specific intervals in the course of the study and serum samples prepared and assayed using the appropriate methods, for chlorine (C1-) sodium (Na+), pottasium (K+), bicarbonate (HC03-), glucose, bilirubin, albumin, serum glutamic oxaloacetic transminase (SGOT) and Total protein (TP) levels. Differences between the control and the x infected groups were significant (p<0.05). The mean albumin levels in the T. vwax group was significantly lower (p<0.05) than those of T. brucei and T. congolense groups. Whilst the mean glucose level in the T. congolense group was also significantly lower (p<0.05) compared to the other infected groups. A significant drop in the values of Na+> CI- and HCG3- levels occured in the T. vivax infected goats. Similarly T. brucei infected group produced drop in the level of albumin, total protein as well as the greatest rise in K+ and SGOT levels. On the other hand, the lowest mean glucose level and highest bilirubin and blood urea Nitrogen levels were observed in the T. congolense group. The study revealed the serious effect of trypanosomosis on the serum biochemical components and therefore an idea of the consequences of the disease on the metabolic activities of affected goats. The role of trypanosome sialidase enzymes in the pathogenesis of anaemia in animal trypanosomosis using the goal as an animal model was evaluated. Significant differences (p<0.001) existed between the mean rbc sialic-acid concentration of the control and infected groups. The greatest fall in rbc sialic-acid concentration or the highest sialidase enzyme cleavage activity occured in the T. vivax group (5.82 ± 0.19 -1.88 ± 0.28 mg/dl or 67.7% reduction) followed by T, brucei (5.85 ± 0.43 to 2.28 ± 0.36 mg/dl or 61.33% reduction) and T. congolense (5.09 ± 0.11 to 3.94 ±0.18 mg’dl or 33.22% reduction). That of the control group was 1.04% reduction (5.78 ± 0.32 to 5.72 ± 0.25 mg/dl). The study further reinforced the reported findings of earlier workers that there is a mammalian blood stream form of sialidase enzyme in T. vivax. It also added weight to the suspicion that though mammalian form of sialidases have not been confirmed in T. brucei and T. congolense, the rbc sialic-acid cleavage activities of these two trypanosome xi species suggest the presence of some forms of sialidase, possibly trans-sialidase which undertake the cleavaging. The study also revealed that sialidase enzyme plays a major role in the pathogenesis of trypanosomosis induced anaemia because of the relationship between fall in rbc sialic acids and consequent tall in rbc and pcv levels in all the infected goats. The results obtained also gave a favourable disposition to the future use of small ruminants in further investigations into the relationship between sialidase enzyme and anaemia of animal trypanosomosis

COMPARATIVE STUDY OF TRYPANOSOMOSIS EXPERIMENTALLY INDUCED IN SAVANNAH BROWN GOATS USING Trypanosoma brucei, Trypanosoma congolense AND Trypanosoma vivax.