Investigations of the occurrence of Avibacterium paragallinarum infections in Uganda.

Investigations were conducted to determine the occurrence of Avibacterium paragallinarum in poultry in Uganda. A total of 710 each of bacteriologic and serum samples were taken from chickens and turkeys for demonstration of A. paragallinarum and antibodies. Samples for isolation of A. paragallinarum were also subjected to direct polymerase chain reaction (PCR) for demonstration of the organism's presence. Antibodies to A. paragallinarum were demonstrated in the sera using the hemagglutination inhibition test. A total of five isolates were recovered from two out of five commercial layer chicken farms investigated where suspected cases of infectious coryza were reported, and all of them belonged to Page's serovar C. PCR detected more positive samples (11/68) than did culture (5/68). Isolates were not recovered from free-range poultry nor were there any positive samples by PCR. The overall seroprevalence was 40.5% and the seroprevalence to serovars A, B, and C were 18%, 0.5%, and 22%, respectively. Antibodies to all Page's serovars A, B, and C were demonstrated in free-range chickens but only serovar C antibodies were demonstrated in commercial chickens. No antibodies were demonstrated in turkeys. This is the first time infectious coryza has been confirmed in Uganda and the causative agent, A. paragallinarum, isolated. A high seroprevalence observed in free-range chickens seems to indicate a subclinical infection under extensive village management conditions.

Virulence characterization of Avibacterium paragallinarum isolates from Uganda.

Avibacterium paragallinarum isolates from Uganda were characterized for their virulence by comparison of their pathogenicity and their resistance to serum. Pathogenicity was evaluated using commercial Hisex Brown layer chickens, local indigenous chickens, local turkeys and local guineafowls inoculated with 108 colony-forming units of Av. paragallinarum and comparing their overall mean disease scores over a period of 20 days. Persistence of the bacteria in the host and water was also investigated for a 60-day period by culture and polymerase chain reaction as well as use of sentinel chickens. Serum resistance was measured by comparison of the growth kinetics and survival indices at 3 and 6 h. There was no difference in the virulence of the isolates. Commercial layer chickens and local indigenous chickens were equally susceptible to challenge, while turkeys and guineafowls only showed transient mild signs and did not transmit infection. Turkeys and guineafowls did not acquire the infection when placed in contact with infected chickens. The isolates were resistant in normal chicken serum at both 3 and 6 h of incubation but were resistant at 3 h and sensitive at 6 h in turkey and guineafowl sera. The resistance of the isolates to serum correlated with their pathogenicity in the different hosts. No carrier status was demonstrated in this study using polymerase chain reaction and culture. The present study demonstrates that Ugandan Av. paragallinarum isolates are pathogenic to chickens with only transient signs in turkeys and guineafowls, and that serum resistance could be a subject for further investigation as a predictor of virulence of these bacteria. The role of turkeys and guineafowls in transmission of Av. paragallinarum was not demonstrated in the present investigation.

The pathogenesis of anaemia in goats experimentally infected with Trypanosoma congolense or Trypanosoma brucei: use of the myeloid:erythroid ratio.

The present study examined the development of anaemia in Small East African goats experimentally infected with Trypanosoma congolense or Trypanosoma brucei. Experimental goats received a primary trypanosome challenge on day 0, treated with diminazene aceturate on day 49 and received a secondary trypanosome challenge on day 77 of the 136-day experiment. Both primary and secondary challenges were characterised by reduced peripheral erythrocyte counts, fall in packed cell volume (PCV), hypohaemoglobinaemia and reductions in the myeloid:erythroid ratios (M:E) compared with the uninfected goats. The progressive reduction in the M:E ratios denoted increased erythrogenesis in response to increased destruction of erythrocytes in blood by infecting trypanosomes or their products. The more rapid fall in M:E ratio in T. congolense infections shows that this parasite causes more severe clinical pathological effects in goats than T. brucei.

Glossina fuscipes fuscipes in the trypanosomiasis endemic areas of south eastern Uganda: apparent density, trypanosome infection rates and host feeding preferences.

A study was undertaken in three districts in south eastern Uganda endemic for human and animal trypanosomiasis, to investigate the status of the vector tsetse fly population. Apparent density (AD) of tsetse was between 2 and 21 flies/trap/day across the three districts, with Glossinia fuscipes fuscipes identified as the predominant species. Trypanosomes were observed in G.f. fuscipes with an infection rate, as determined by microscopy, of 1.55% across the three studied areas. However, trypanosome infections were only identified in female flies giving an infection rate of 2.39% for the female tsetse when this sex was considered in isolation; no male flies were found to be infected. Bloodmeal analysis highlighted 3 principal vertebrate hosts, namely cattle, pigs and monitor lizards (Varanus niloticus). The implication of this, in relation to the cycle of transmission for human infective trypanosomes between domestic animals and man, is discussed.

Bovine trypanosomiasis in south-western Uganda: packed-cell volumes and prevalences of infection in the cattle.

Following confirmed cases of trypanosomiasis ('nagana') and reports of trypanosome-attributable deaths among local cattle, a cross-sectional study was undertaken to determine the prevalence of bovine infection with trypanosomes in south-western Uganda. Cattle from 10 different localities were checked by the microscopical examination of wet bloodsmears and thin, stained bloodsmears, and by blood centrifugation followed by the examination of the resultant buffy coats. Of the 1309 cattle investigated, 6.42% (5.56% and 7.26% of those from the Mbarara and Mubende districts, respectively) were found to be infected. Of the positive animals, 71 (84.5%), 11 (13.1%) and two (2.4%) appeared to be infected with Trypanosoma vivax only, T. congolense only and both T. vivax and T. congolense, respectively. The prevalence of infection with T. vivax was significantly higher than that with T. congolense (P<0.001). The mean packed-cell volumes (PCV) for the trypanosome-positive animals were lower than those for the trypanosome-negative, whether the cattle considered were all those investigated (22.3% v. 29.0%; P<0.001) or just those from the Mbarara (22.8% v. 28.2%) or Mubende (21.5% v. 29.7%) districts. South-western Uganda has been relatively free of both human and bovine trypanosomiasis for the past three decades. The factors leading to the current resurgence of bovine trypanosomiasis need further investigation.

Domestic animals as reservoirs for sleeping sickness in three endemic foci in south-eastern Uganda.

The persistence of sleeping sickness (human African trypanosomiasis) in some areas of south-eastern Uganda has necessitated further investigations, focusing mainly on domestic animals as reservoirs of this disease in three agro-ecological zones. The inter-zone differences in the prevalences of trypanosome infection among cattle (P < 0.001) and pigs (P < 0.001) were significant. Overall, 5.0% of the cattle, 13.9% of the pigs and 0.4% of the small ruminants investigated were found to be infected with parasites of the Trypanosoma brucei subgroup. The results of blood incubation infectivity tests (BIIT) indicated that all of the T. brucei-subgroup isolates from cattle in Kamuli district (zone I) were human-serum-sensitive. Of the zone-I pigs found infected, however, almost all (82.5%) were considered to be infected with T. brucei and many (30.2%) carried human-serum-resistant T. brucei. Pig-tsetse-human appears to be a major transmission cycle in zone I. In Mukono district (zone II), 10.5% and 26.1% of the T. brucei isolates from cattle and pigs, respectively, were human-serum-resistant, indicating that cattle-tsetse-human and pig-tsetse-human are major transmission cycles in zone II. In Tororo district (zone III), 47.3% of the T. brucei isolates from cattle were human-serum-resistant but there were no T. brucei isolates from pigs, indicating that cattle-tsetse-human is the major transmission cycle. Interestingly, as the only T. brucei isolate from sheep in zone III was human-serum-resistant, there may also be a sheep-tsetse-human cycle. In south-eastern Uganda, control efforts must be designed to eliminate the parasites not only from cattle but also from pigs and small ruminants.

Impact of nutrition on the pathophysiology of bovine trypanosomiasis.

Trypanosomiasis is a major veterinary problem over much of sub-Saharan Africa and is frequently associated with under-nutrition. There is growing evidence that nutrition can have a profound effect on the pathophysiological features of animal trypanosomiasis. These features include anaemia, pyrexia, body weight changes, reduced feed intake and diminished productivity including reduced draught work output, milk yield and reproductive capacity. Anaemia is a principal characteristic of trypanosomiasis and the rate at which it develops is influenced by both protein and energy intakes. Pyrexia is associated with increased energy demands for maintenance which is ultimately manifested by reductions in voluntary activity levels and productivity. Weight changes in trypanosomiasis are markedly influenced by the levels of protein intake. High intakes allow infected animals to grow at the same rate as uninfected controls providing energy intake is adequate whilst low energy levels can exacerbate the adverse effects of trypanosomiasis on body weight. Reductions in feed intake are less apparent in animals which are provided with high protein diets and where intake is limited by the disease animals will often exhibit preferential selection of higher quality browse. Further studies are required to evaluate the minimum levels of protein and energy supplementation required to ameliorate the adverse effect of trypanosomiasis, the nature and quality of protein supplement to achieve these benefits and the influence these have on digestive physiology.

The influence of energy intake on some blood biochemical parameters in Scottish Blackface sheep infected with Trypanosoma congolense.

The intensity of parasitaemia, degree of anaemia, live body weight gains and blood biochemical changes were measured in two groups of Scottish Blackface sheep infected experimentally with Trypanosoma congolense and allowed either a high (9.9 MJ metabolisable energy (ME) per day) or a low (6.1 MJ ME per day) energy intake. It was observed that infected animals on the low energy intake had a longer mean prepatent period, but following patency they developed more severe anaemia and greater growth retardation than those on the high energy intake. Both infected groups exhibited significant reductions in serum total lipids, phospholipids, plasma cholesterol and albumin. However, these changes were more severe in the animals on the low energy intake than in those on the high energy intake. It was concluded that adequate energy nutrition enhances the ability of infected animals to withstand the adverse effects of infection by promoting body weight gains and moderating the severity of the pathophysiological changes associated with ovine trypanosomosis.

Polymerase chain reaction and DNA probe hybridization to assess the efficacy of diminazene treatment in Trypanosoma brucei-infected cattle.

Four of eight Ankole longhorn cattle experimentally infected with Trypanosoma brucei were treated with 7 mg/kg diminazene aceturate (Berenil, Hoechst AG, Germany) at day 71 postinfection. The trypanocidal activity was monitored using polymerase chain reaction (PCR) and DNA probe hybridization. When extracted parasite DNA (without host DNA) was used, as little as 1 fg per reaction, which is equivalent to about 1-10% of the DNA in a single trypanosome, produced a specific product that was visible as a 177-bp band in an agarose gel. In infected cattle, specific PCR products could be amplified at as early as 1 day postinfection. PCR signals remained positive during infection, except in one sample, although aparasitemic phases occurred. In cases where treatment resulted in a significant clinical improvement, PCR signals disappeared at 3-4 days after the administration of the drug. By contrast, in cattle that showed clinical signs of CNS involvement after treatment, although aparasitemic, and died before the termination of the experiment, specific products could be amplified on several occasions following treatment. The PCR signals generated after treatment could be further enhanced by subsequent slot-blot hybridization with a T. brucei-specific DNA probe. We conclude that PCR coupled with DNA probe hybridization provides a highly sensitive tool for the assessment of therapeutic efficiency and disease progression in trypanosome infections, especially in chronic infections when the level of parasitemia is low or when trypanosomes are sequestered at cryptic sites.

The influence of supplementation with cotton seed cake on the resistance of Ugandan goats to primary and secondary challenges with Trypanosoma congolense and on their response to treatment.

The present study investigated the influence of supplementation with cotton seed cake on the resistance of the Small East African breed of goats to primary and secondary challenges with Trypanosoma congolense and on their response to chemotherapy with diminazene aceturate. The supplemented group received 300 g of cotton seed cake per day in addition to about 500 g of fresh napier grass which was available to the unsupplemented group. It was observed that the supplemented infected (SI) group tended to sustain higher intensities of parasitaemia than the unsupplemented infected (USI) group particularly during the primary challenge and both groups showed longer prepatent periods to secondary challenge than to primary challenge. Infection caused a significant reduction in the rate of live body weight gain in the USI group compared with the unsupplemented control (USC) group whilst the SI group grew at the same rate as the supplemented control (SC) group. This effect was observed both during primary and secondary challenges. Following primary challenge, both infected groups developed similar degrees of anaemia, but the packed red cell volume (PCV) levels in the SI group improved towards the end of the first challenge and were also significantly higher than those of the USI group during the second challenge. After treatments at 56 and 126 days after infection (DAI), the greatest response was observed in PCV values. The response of the SI group was superior to that of the USI group and by 4 weeks after treatment the PCV values of the SI and SC groups were similar while those of the USI group were significantly lower than those of the USC group. It is concluded that supplementation with cotton seed cake plays an important role in the rate of live weight gain, and rate of recovery from anaemia produced by trypanosome infection in goats.

Susceptibility of three breeds of Ugandan goats to experimental infection with Trypanosoma congolense.

This study has indicated that differences in susceptibility to Trypanosoma congolense infection exist among the 3 main breeds of goats in Uganda namely, Kigezi, Mubende and Small East African (SEA). The Kigezi goats appeared to be the most susceptible suffering more severe anaemia, greater retardation of growth and more deaths than the other 2 breeds following experimental infection with Try-panosoma congolense. The Small East African goats appeared to be least susceptible. Following treatment after 84 days of infection, the SEA goats responded much better than the other 2 breeds. By 4 weeks after treatment with diminazene aceturate, the packed red cell volumes of the treated SEA goats were similar to those of control SEA goats while those of the Mubende and Kigezi goats were still much lower than those of control animals.

Pathophysiology of Trypanosoma congolense infection in two breeds of sheep, Scottish blackface and Finn Dorset.

The pathophysiology of Trypanosoma congolense infection was studied in two breeds of sheep, the Scottish Blackface (SB) and Finn Dorset (FD), which were known from previous studies to differ significantly in their susceptibility to haemonchosis, in which anaemia is also the primary pathophysiological effect. It was found that infected SB and FD lambs developed similar intensities of parasitaemia. However, infected SB lambs developed a higher degree of anaemia, more severe thrombocytopaenia and hypoalbuminaemia than infected FD. Following infection, the concentrations of plasma cholesterol, serum phospholipids and total lipids decreased. The decline in these lipid components appeared to be greater in infected SB than in infected FD lambs.

The influence of dietary protein on some blood biochemical parameters in Scottish blackface sheep experimentally infected with Trypanosoma congolense.

The present study investigated the influence of dietary protein on some blood biochemical parameters, namely lipids, proteins, iron, glucose and B-hydroxybutyrate, in Scottish Blackface sheep infected with Trypanosoma congolense, and given either a low protein (51.5 g digestible crude protein per day) or a high protein (116 g digestible crude protein per day) diet. Both low and high protein diets were isocaloric and animals were monitored for 10 weeks after infection. It was observed that infection was associated with marked reduction in the concentrations of plasma total lipids, cholesterol, phospholipids and non-esterified fatty acids in both dietary groups. Control animals on a high protein diet had higher concentrations of plasma total lipids and cholesterol than those on a low protein diet. Infection caused severe hypoalbuminaemia and reduction in total iron-binding capacity only in the low protein infected group compared to their controls while the changes in the high protein infected and control groups were similar. Control animals receiving a high protein diet had higher concentrations of plasma albumin and total iron-binding capacity than those receiving a low protein diet. These observations suggest that Trypanosoma congolense infection in sheep is associated with marked changes in blood biochemical parameters, some of which are influenced by dietary protein.

The influence of dietary protein on live bodyweight, degree of anaemia and erythropoietic responses of Scottish blackface sheep infected experimentally with Trypanosoma congolense.

The present study investigated the influence of dietary protein on the intensity of parasitaemia, degree of anaemia and erythropoietic responses, in sheep experimentally infected with Trypanosoma congolense and given either a high protein diet (116 g digestible crude protein [DCP] per day) or a low protein diet (51.5 g DCP per day). It was observed that infected and control animals on the high protein diet grew at similar rates while infected animals on the low protein diet experienced marked retardation of growth compared with their uninfected controls. Dietary protein had no influence on the degree of anaemia that followed infection. Measurement of blood volumes revealed that low protein infected group had significantly lower mean circulating red cell volume than their controls. Ferrokinetic measurements indicated that plasma iron turnover rates (PITR) and 59Fe incorporation rates were higher in the high protein infected group than in the low protein infected group, although these differences were not significant. These observations indicate that infected animals on a high protein tended to show greater enhancement of erythropoietic activity that infected animals on low protein diet.

Tsetse survey in Mukono district, south-east Uganda: population structure, distribution and blood meal status.

The population structure, feeding state and distribution of tsetse of Glossina fuscipes fuscipes species in Ssugu parish of Mukono district, south-east Uganda were investigated. Tsetse caught with pyramidal traps were counted, sexed and dissected for age grading. It was observed that most tsetse were caught in valley habitats in the dry season, but the distribution was almost uniform within the parish in the wet season. The apparent density and prevalence of blood meals in tsetse fluctuated in different months. There were more males with a fresh blood meal than females (P < 0.05). In the population there was a preponderance of young tsetse of less than 60 days. There were significantly more teneral males than teneral females (P < 0.05). In all months the percentage of females was higher than that of males and ranged between 51.1% to 64.6 per cent. The epidemiological implications of these findings are that the risk of contracting trypanosomosis is high during the period of uniform distribution; since this is associated with an increase in apparent density and therefore high man-tsetse-animal contact. Furthermore, these results have shown that it is possible to prevent increase in the population of tsetse by applying insecticides on animals and targets in September and early October, since recruitment in tsetse population follows the rains.

The prevalence of trypanosomosis in small ruminants and pigs in a sleeping sickness endemic area of Buikwe County, Mukono district, Uganda.

A survey of trypanosomosis in goats, sheep and pigs was carried out in Buikwe County, Mukono District of South Eastern Uganda between April and August 1994. Infection rates of 8.8% in 204 goats, 26.7% in 60 sheep and 32.4% in 68 pigs of all ages and both sexes were recorded. Trypanosoma brucei parasites were found in goats and pigs, T. congolense in sheep and pigs and T. vivax in goats and sheep. Infection rates were similar in both sexes of animal species and it was observed that T. vivax caused high levels of parasitaemia while T. brucei infections were associated with very low levels of parasitaemia. Trypanosoma brucei infections accounted for 66.7% and 30% of all infections in goats and pigs, respectively. It is postulated that some of these T. brucei parasites could be T. b. rhodesiense, the causing agent of sleeping sickness in this area.

Effect of nutritional level on bodyweight, degree of anaemia and carcase composition of sheep infected with Trypanosoma congolense.

The influence of nutritional level on the bodyweight, degree of anaemia and carcase composition of 24 sheep infected experimentally with Trypanosoma congolense was investigated. The infection caused a marked retardation of growth in the animals fed a low protein ration whereas the infected and control animals fed a high protein ration grew at similar rates. Both groups of infected animals developed similar degrees of anaemia but the infected group fed the high protein diet tended to sustain a higher intensity of parasitaemia than the group fed the low protein diet. The infection was also associated with low killing out percentages and a general reduction of total carcase protein, energy and fat. The decline in these carcase components was greater in the animals fed the low protein diet than in those receiving the high protein diet.

Influence of Trypanosoma congolense infection on some blood inorganic and protein constituents in sheep.

The present study was designed to investigate the changes in plasma concentrations of zinc, copper, calcium, magnesium, inorganic phosphate, total protein, albumin, globulin, and serum iron and iron-binding capacity in sheep infected with Trypanosoma congolense. It was observed that infection did not have a significant effect on the plasma concentrations of zinc, copper, calcium, magnesium and inorganic phosphate. The serum iron concentrations in infected animals were higher, but not significantly so, than in control animals. Infected animals developed hypoalbuminaemia and hyperglobulinaemia while changes in total protein were not significant. The relevance of these changes to the pathogenesis of Trypanosoma congolense infection is discussed.

The influence of energy intake on the pathophysiology of Trypanosoma congolense infection in Scottish blackface sheep.

The intensity of parasitaemia, degree of anaemia, live body weight gains and blood biochemical changes were measured in two groups of Scottish Blackface sheep infected experimentally with Trypanosoma congolense and allowed either a high (9.9 MJ metabolisable energy (ME) day-1) or a low (6.1 MJ ME day-1) energy intake. It was observed that infected animals on the low energy intake had a longer mean prepatent period, but following patency they developed more severe anaemia and greater growth retardation than those on the high energy intake. Both infected groups exhibited significant reductions in serum total lipids, phospholipids, plasma cholesterol and albumin. However, these changes were more severe in the animals on the low energy intake than in those on the high energy intake. It was concluded that adequate energy nutrition enhances the ability of infected animals to withstand the adverse effects of infection, by promoting body weight gains and moderating the severity of the pathophysiological changes associated with ovine trypanosomosis.