| Livestock Research for Rural Development 29 (5) 2017 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
Area Wide Integrated Pest Management (AW-IPM) programme using Sterile Insect Technique (SIT) depends on a reliable supply of large numbers of high quality sterile insect for release. Vector and Vector Borne Disease Institute (VVBD) is currently rearing G. pallidipes, G. austeni and G. brevipalpis mainly for research and eradication purposes. However, the production of the species mentioned above is still low, therefore the institute decided to start collection of wild flies for the purpose of boosting their production in the laboratory. The collection of wild flies was done at Msubugwe game reserve in Pangani district. A total of 31 pyramidal traps baited with acetone and cow urine were deployed in the collection area.
The average catches per day were 200 female G. pallidipes and 10 female G. brevipalpis. Immediate after collection flies were fed on goats then transported to the institute for rearing. A total of 6,038 female of G. pallidipes and 911 female of G. brevipalpis were adapted in the laboratory. In the laboratory, G. brevipalpis had an average mortality of 1.3± 0.23% with fecundity of 0.6± 0.05 per week and G. pallidipes had an average mortality of 3.1 ± 0.32% with fecundity of 0.2± 0.03 per week. The mortality of G. brevipalpis was slightly higher (P < 0.001) than the recommended which is ≤ 1% but its fecundity was very good as it was above the recommended fecundity. However G. pallidipes had significant higher (P < 0.001) mortality with very low fecundity. The average pupae produced per week by G. brevipalpis was 48± 9.71 from an average of 485 females and that of G. pallidipes was 25± 2.77 from an average of 57 females. Generally G. brevipalpis performed better than G. pallidipes in the laboratory; there was significant increase on the production of the specie in the laboratory.The poor performance observed in G. pallidipes could be due to viral ( Salivary gland hyperplasia virus) infection which is known to affect the reproductive performance of the specie.
Key words: performance, Sterile Insect Technique (SIT)
Thirty three percent of arable land of Tanzania is infested with tsetse flies which transmit trypanosomes which affect livestock development and human health in the country (Daffa et al 2013). The flies transmit trypanosomes that cause sleeping sickness to human and nagana to livestock. The losses suffered annually in cattle due to the disease in terms of mortality, morbidity and reduced milk yield is estimated to be 4.5 billion Tanzanian Shillings (US$2.3 million) (Shaw et al 2014). About four million people are at risk of human trypanosomiasis infection where less than 100 sleeping sickness cases are reported annually in the country (Simarro et al 2010).Tsetse control efforts have been undertaken throughout the African continent but long term and sustainable control has rarely achieved.Tsetse control efforts invariably are tied to the complex problems of poverty, health, politics and violence which have been proved such a disaster for the African peoples. Past attempts to control tsetse flies in the continent were ground insecticide spraying, bush and game clearance, sequential aerial spraying (SAT) and the use of traps and targets (Kuzoe and Schofield 2004). However, there are limitations to the use of each of the method. Lack of sustainability of some techniques used has led to the controlled area to be re-infested. Experience has shown that protection of even small areas located within a major tsetse belt by regular tsetse control intervention measures is uneconomical. The most viable choice is to employ the area wide approaches, targeting the entire tsetse population in a given area and eliminate it. There are several examples of past successful area wide pest and vector management programmes. One example of African programme which was successful was Sterile Insect Technique (SIT) which eradicated G. austeni in Zanzibar Island in 1997 (PATTEC 2001). Area wide Integrated Pest Management (AW-IPM) programme using the Sterile Insect Technique (SIT) depends on reliable supply of large numbers of high quality sterile insect for release (Abd-Alla et al 2006). Vector and Vector Borne Disease Institute is currently rearing G. pallidipes, G. austeni and G. brevipalpis in the laboratory for eradication and research purposes. However, the production of G. pallidipes and G. brevipalpis in the laboratory is still low, therefore the institute decided to start collection of wild flies for the purpose of boosting their production in the laboratory. The performance of these two tsetse species in the laboratory is reported.
Wild flies were collected at Msubugwe game reserve which is situated about 60 km southern of the institute in Pangani district -Tanga region. Fly trapping was done at the end of rain season July. A total of 31 pyramidal traps baited with acetone and cow urine were deployed in the collection area as described by Vale, 1998. Traps were deployed under the shade in order to avoid high temperature which could affect the physiology of the trapped flies. Immediately after collection, flies were fed on goats then parked in the cool box and transported to the institute in air conditioned car for rearing. Mercury thermometer was used to monitor temperature during fly transportation. In the laboratory flies were maintained at a temperature which varied from 23.5OC to 24OC with relative humidity varying from 75% to 80% for three months. Pupae produced by flies were taken to the insectary to boost colony performance of G. pallidipes and G. brevipalpis.
The average catches per day were 200 female G. pallidipes and 10 female G. brevipalpis; very few G. m. morsitans were also caught. Generally more females flies were caught compared to male tsetse flies. Survival rate of the wild flies improved by 75% when flies were fed immediately on goats (in vivo) than when they were transported to the institute without feeding on goats. At the institute, flies were fed using in vitro feeding system. A total of 6,038 female of G. pallidipes and 911 female of G. brevipalpis were adapted in the laboratory. Performance of these species in the laboratory is summarized in the table 1 below.
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Table 1. Performance of wild G. pallidipes and G. brevipalpis in the laboratory |
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Tsetse specie |
Average pupae |
Average |
Average |
|
G. pallidipes |
48± 9.71 |
0.2± 0.03 |
3.1± 0.32% |
|
G. brevipalpis |
25± 2.77 |
0.6± 0.05 |
1.3± 0.23% |
|
t-test |
4.5* |
2.3** |
6.0*** |
|
* = significant at (P < 0.05), *** = significant at (P < 0.001) |
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Table 1 above shows G. brevipalpis had an average daily mortality of 1.3 ± 0.23% with fecundity of 0.6 ± 0.05 per week and G. pallidipes had an average daily mortality of 3.1 ± 0.32% with mean fecundity of 0.2 ± 0.03 per week in the laboratory. The average pupae production per week of G. brevipalpis was 25 ± 2.77 from an average of 57 females and that of G. pallidipes was 48 ± 9.71 from an average of 319 females. The average daily mortality of G. brevipalpis was slightly higher (P < 0.001) than the recommended fecundity which is ≤ 1% but its fecundity was very good as it was above the recommended fecundity. However G. pallidipes had significantly higher (P < 0.001) mortality with very low fecundity when comparison was made between the two species. The average pupae produced by G. brevipalpis (25 ± 2.77) were significant higher (P < 0.005) than the one produced by G. brevipalpis (48 ± 9.71).
The present findings of this small study shows that wild G. brevipalpis performed well in the laboratory compared to wild G. pallidipes. The specie had significant lower mortality with higher mean fecundity per week. Fecundity of this specie was good as it was above the recommended fecundity which is ≤ 0.6. However, its mortality was slightly higher 1.3 ± 0.32% than the recommended one which is ≤ 1%. The good performance shown by G. brevipalpis had a significant impact on the production of G. brevipalpis in the laboratory. The poor performance shown by wild G. pallidipes may be due to sensitivity of the specie to environmental changes. This is justified by observations made when the flies were brought to the laboratory didn’t feed well compared to G. brevipalpis which fed well. Another possible reason might be the viral infection ( Salivary gland hyperplasia virus) which affects the reproductive performance of flies in the laboratory. It has been reported that the pathological effect of the virus is more severe in G. pallidipes than other tsetse species (Abd-Alla et al 2006). Some tsetse species perform better than others in terms of survival and reproductive performance while colonization of some species such as that of G. pallidipes, has so far been unsuccessful in the laboratory.
I would like to express my thanks to the Ministry of Livestock Development and Fisheries for funding this small study. Full participation given by VVBD staffs during fly collection and rearing is highly appreciated.
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Received 8 July 2016; Accepted 18 February 2017; Published 1 May 2017