Entomological findings
A total of 5,003 tsetse flies, G. pallidipes (99.5%) and G. fuscipes (0.5%), were captured in communities within and around QENP with other biting flies (n = 20,237) (Table 1). BT traps caught both G. pallidipes (99.3%) and G. fuscipes (0.67%) while F3 traps caught only G. pallidipes. The biting flies were mainly in the genus of Stomoxys, Tabanids, Muscids, Hymenopteran and Lepidopterans. Stomoxys had the highest number among other biting flies captured (Table 1).
Table 1
Frequency of Tsetse fly species and other biting flies captured in and around QENP
Type of Fly | Sex | Total |
Male | Female |
No. (%) | No. (%) |
Tsetse fly | | | |
G. pallidipes | 368 (7%) | 4,611 (93%) | 4,979 |
G. fuscipes | 7 (29%) | 17 (71%) | 24 |
Other Biting flies* | | | |
Stomoxys | - | - | 18,310 |
Tabanids | - | - | 428 |
Muscids | - | - | 278 |
Hymenopteran | - | - | 117 |
Lepidopterans | - | - | 14 |
*No sex determination was done for other biting flies. |
The computed apparent fly density (FTD), the average number of flies caught per trap per day for the entire surveyed area was 20.6. BT traps caught a total of 3,566 tsetse flies with an average of 63.67 and the FTD of 21.22 tsetse flies per day while F3 caught a total of 1,437 tsetse flies with an average of 62 and FTD of 21 tsetse flies per day (Table 2).
Table 2
Tsetse fly and Biting flies caught per trap type in different communities around QENP
Community Site | Type of Trap | No. of Traps | Tsetse flies/trap | Other biting flies | FTD | Mean ± SE* |
Hamukungu | BT | 10 | 2278 | 282 | 74.3 | 222.87 ± 50.6 |
F3 | 5 | 1065 | 275 |
Nyakatonzi | BT | 9 | 1187 | 10068 | 38.1 | 114.23 ± 40.3 |
F3 | 4 | 298 | 1832 |
Karusandara | BT | 9 | 31 | 2601 | 0.9 | 2.79 ± 1.68 |
F3 | 5 | 8 | 2601 |
Muhokya | BT | 9 | 61 | 447 | 1.7 | 5.08 ± 2.55 |
F3 | 4 | 5 | 65 |
Ibuga | BT | 10 | 1 | 1389 | 0 | 0.07 ± 0.07 |
F3 | 5 | 0 | 393 |
Busunga | BT | 9 | 8 | 245 | 2.1 | 6.27 ± 3.756 |
F3 | 2 | 61 | 39 |
Totals | | 81 | 5003 | 20237 | 20.6 | |
FTD - Apparent fly density; BT and F3 - Types of Tsetse fly traps; CI – 95% CI for mean; *Mean number of Tsetse flies caught in each community (SE - Standard Error)
Hamukungu community had significantly higher numbers (p = 0.001) of tsetse flies caught than in the rest of the communities (Table 2). Glossina fuscipes was captured only in Nyakatonzi community along River Nyamugasani that has a marshy riverine forest/woodland vegetation along the river banks (Fig. 1). Figure 1 was developed by authors. the The mean numbers of G. pallidipes (61.5 ± 14.7) captured were significantly higher than that of G. fuscipes (0.3 ± 0.2) in the whole study area (p = 0.001). There was significantly higher apparent density (FTD) of G. pallidipes caught by BT than the G. fuscipes captured by the same trap type (F-Statistic = 48.4, p = 0.001). There was no G. fuscipes trapped by F3 trap but still there was a statistically significant difference for FTD between G. pallidipes and G. fuscipes (F- Statistic = 16.4, p = 0.031).
Furthermore, the results showed a significant difference in the number of tsetse flies caught in different vegetation types in the study area (F – Statistic = 8.56, p = 0.001). Thickets and shrubs had significantly higher numbers of tsetse flies trapped than those trapped in the open savannah grasslands (D = 138.465, p = 0.001) and marshy riverine woodland (D = -138.0, p = 0.002). However, the difference was not statistically significant with grassland and thickets (D = 98.444, p = 0.198). There was a significant difference in the number of tsetse flies caught in different vegetation types in the study area (Post hoc Analysis F = 8.56, p = 0.001). Marshy riverine woodland had significantly higher number of tsetse flies than open savannah grasslands (D = 271.3, p = 0.001) and grassland and thickets (D = 231.3, p = 0.001).
Trypanosomes in cattle and goat blood samples collected in June 2015
In 2015, a total of 445 blood samples were collected from both cattle and goats with 71.7% (n = 319) of the samples being goats. Three types of Trypanosoma species, namely T. brucei (480 bp), T. congolense (700 bp) and T. vivax (250 bp) were got using PCR (Fig. 2).
s1 to s11 correspond to test samples positive for trypanosomes and N indicates the Negative control while P1 is positive control for T. brucei, P2; positive control for T. vivax and P3 is positive control for T. congolensis. 700 bp indicates T. congolensis, 480 bp indicates T. brucei and 250 bp represents T. vivax. Sample (s6) is positive for both T. congolensis and T. brucei. DNA ladder (100 bp) was used as indicated on the gel above.
The overall prevalence of Trypanosoma spp in cattle and goat blood samples collected in 2015 was 38.9% and 37% respectively. However, the prevalence in cattle was not significantly different from that of goats (F = 1.654, p = 0.4870). Trypanosoma brucei was the highest prevalent trypanosome in both cattle (23%) and goats (18.8%), followed by T. congolense while T. vivax was the least prevalent trypanosome in both animal species (Fig. 3).
Figure 3. Prevalence of Trypanosoma spp in cattle and goats in 2015
The proportion of animals with single infection was higher than for mixed infection in both cattle and goats (Fig. 4). In both cattle and goats, a mixed infection of T. brucei + T. congolense was most encountered with prevalence rates of 4.8% (n = 6/126) and 4.1% (n = 13/319) in cattle and goats, respectively (Fig. 4). Also, in cattle, a mixed infection of T. brucei + T. vivax was higher (3.2%, n = 4/126) than in goats (0.6%, n = 2/319) whereas in goats a mixed infection of T. brucei + T. congolense + T. vivax was higher (2.8%, n = 9/319) than in cattle (2.4%, n = 3/126) (Fig. 4).
Kashaka landing site (50%, n = 25/50) had the highest Trypanosoma infection rates followed by Kisenyi landing site (43.9%), Rwenshama (33.1%) and lowest in Kirugu sub-county (32.6%). While the prevalence was high in Kashaka fish landing site (Table 3), the difference compared to other areas was not statistically significant (p = 0.106). Cattle in Nyakatonzi community had a trypanosome prevalence of 38.9%.
More males among cattle were observed to have higher trypanosome prevalence (47.8%) than female (36.9%). On the contrary, female goats (37.8%) had a higher prevalence of trypanosomes than the males (33.3%) (Table 3). However, in as much as the prevalence were different, these differences were not statistically significant in both sexes (Cattle: F [36.9, 47.8] = 2.76, p = 0.245]; Goats [F (37.8, 33.3) = 1.95, p = 0.143]). The prevalence of trypanosomes among cattle was higher in adults (44.3%, n = 31/70) than in sub-adults (32.1%, n = 18/56). However, the difference wasn’t statistically significant at p > 0.05 (F = 2.62, p = 0.094). There were no young cattle tested.
Table 3
Prevalence of Trypanosoma spp in cattle and goats in Year 2015
Category | Prevalence (%) in Cattle | | Prevalence (%) in Goats |
| No.* | T. congolense | T. brucei | T. vivax | P# | No.* | T. congolense | T. brucei | T. vivax | P# |
Location | | | | | | | | | | | |
| Kashaka | - | - | - | - | - | 50 | 12.0 | 16.0 | 34.0 | 50.0 |
Kirugu | - | - | - | - | - | 89 | 10.1 | 19.1 | 6.7 | 32.6 |
Kisenyi | - | - | - | - | - | 41 | 31.7 | 22.0 | 19.5 | 43.9 |
Rwenshama | - | - | - | - | - | 139 | 18.7 | 18.7 | 7.2 | 33.1 |
Nyakatonzi | - | 12 | 17.5 | 23.0 | 11.1 | 38.9 | - | - | - | - |
Sex | Male | 23 | 17.4 | 39.1 | 0.0 | 47.8 | 57 | 10.5 | 26.3 | 3.5 | 33.3 |
Female | 103 | 17.5 | 19.4 | 13.6 | 36.9 | 262 | 18.3 | 17.2 | 14.9 | 37.8 |
Age | Adult | 70 | 21.4 | 22.9 | 11.4 | 44.3 | 186 | 17.2 | 17.2 | 12.4 | 34.4 |
Sub-adult | 56 | 12.5 | 23.2 | 10.7 | 32.1 | 131 | 16.8 | 20.6 | 13.7 | 40.5 |
Young | - | - | - | - | - | 2 | 0.0 | 50.0 | 0.0 | 50.0 |
*Data represents percentages of number of positives for Trypanosomes; # Represents overall prevalence per category. |
Trypanosoma spp in cattle blood samples collected in May 2017
A total of 250 blood samples were collected from cattle in May 2017. No blood samples were collected from goats during this time. The Packed Cell Volume (PCV) ranged from 17–40%. The average PCV of the sampled cattle was 29.1%. The mean PCV value for infected cattle (n = 89) was 29% while the mean PCV value for the non-infected cattle (n = 149) was 29.1%. Approximately 71.8% (n = 171) of cattle sampled had PCV of less than 32% (anemic) while the rest of the cattle had PCV of ≥ 32% (non-anemic). There were no significant differences between the mean PCV of infected and non-infected cattle at 5% level of significance (p > 0.892).
The overall prevalence of Trypanosoma spp was 38%, 1.2%, 1.2% and 2.4% for PCR, thin smear, thick smear and buffy coat diagnostic techniques, respectively. There was a statistically significant difference in the trypanosome prevalence detection by the different techniques (p = 0.000). Post-hoc analysis revealed that detection by PCR was significantly higher than the other techniques (p = 0.000). Based on PCR, the prevalence for T. congolense (n = 80, 32.4%), T. vivax (n = 17, 6.8%) and T. brucei (n = 16, 6.4%) were statistically different (F = 12.76; p < 0.002). Post hoc analysis showed that T. congolense was significantly more prevalent than T. brucei and T. vivax. A co-infection of T. brucei and T. congolense was most encountered in the study area (n = 19; 7.4%). Only 3.2% (n = 8) of the cattle were co-infected with all the three Trypanosome species. There was no mixed infection of T. brucei and T. vivax recorded in the study area for this period.
By individual location, the prevalence of trypanosomes was high in Muhokya (56.3%; n = 27) followed by Lake Katwe (42.9%, n = 15) and less prevalent in Kahendero (24.1%, n = 13). The prevalence of T. congolense was highest in all the sub-counties of study followed by T. vivax (except in Nyakatonzi) while T. brucei was least prevalent (Table 4). There was a significant difference in prevalence of trypanosomes by location (p = 0.039). Using the Post-hoc analysis, Muhokya was found to have a significantly higher prevalence than Kahendero (p = 0.001). There was no significant difference in prevalence of Trypanosoma spp between Muhokya, Karusandara, Lake Katwe and Nyakatonzi (p > 0.05).
Comparing sex, the prevalence of Trypanosoma spp. was not significantly different between female cattle (36.8%, n = 84/228) and male cattle (27.3%, n = 6/22) (p = 0.513) (Table 4). The overall prevalence of Trypanosoma spp was higher in adult cattle (37.1%, n = 75) than in young ones (31.3%, n = 15) though this was not statistically significant (Independent T- test, p = 0.062). The prevalence of Trypanosoma spp was high in local breeds (38.1%, n = 69) followed by cross breeds (37.1%, n = 23) and least prevalent in Friesian breeds (14.3%, n = 1). There was no case of T. brucei recorded in the Friesian breeds. In as much as the prevalence differed among the cattle breeds, there was a strong association (F = 0.736, p = 0.001).
Table 4
Prevalence of Trypanosoma spp in cattle in May 2017
Category | | Prevalence (%) |
No.# | T. congolense | T. brucei | T. vivax | Overall* |
Sub-county | Kahendero | 54 | 18.5 | 3.7 | 5.6 | 24.1 |
Karusandara | 35 | 37.1 | 8.6 | 11.4 | 37.1 |
L. Katwe | 35 | 37.1 | 5.7 | 8.6 | 42.9 |
Muhokya | 48 | 47.9 | 4.2 | 6.3 | 56.3 |
Nyakatonzi | 78 | 28.2 | 10.3 | 5.2 | 34.6 |
Sex | Male | 22 | 27.3 | 4.5 | 4.5 | 27.3 |
Female | 228 | 32.9 | 7 | 7 | 36.8 |
Age | Young | 48 | 29.2 | 4.1 | 8.2 | 31.3 |
Adult | 202 | 33.2 | 7.4 | 6.4 | 37.1 |
| Local | 181 | 32.6 | 7.7 | 6.6 | 38.1 |
Breed | Cross | 62 | 33.9 | 4.8 | 6.5 | 37.1 |
Friesian | 7 | 14.3 | 0 | 14.3 | 14.3 |
# - Number of cattle sampled per category; *Overall prevalence