Prevalence of trypanosomes,salivary gland hypertrophy virus and <Emphasis Type="Italic">Wolbachia</Emphasis> in wild populations of tsetse flies from West Africa

Background

Tsetse flies are vectors of African trypanosomes, protozoan parasites that cause sleeping sickness (or human African trypanosomosis) in humans and nagana (or animal African trypanosomosis) in livestock. In addition to trypanosomes, four symbiotic bacteria Wigglesworthia glossinidia, Sodalis glossinidius, Wolbachia, Spiroplasma and one pathogen, the salivary gland hypertrophy virus (SGHV), have been reported in different tsetse species. We evaluated the prevalence and coinfection dynamics between Wolbachia, trypanosomes, and SGHV in four tsetse species (Glossina palpalis gambiensis, G. tachinoides, G. morsitans submorsitans, and G. medicorum) that were collected between 2008 and 2015 from 46 geographical locations in West Africa, i.e. Burkina Faso, Mali, Ghana, Guinea, and Senegal.

Results

The results indicated an overall low prevalence of SGHV and Wolbachia and a high prevalence of trypanosomes in the sampled wild tsetse populations. The prevalence of all three infections varied among tsetse species and sample origin. The highest trypanosome prevalence was found in Glossina tachinoides (61.1%) from Ghana and in Glossina palpalis gambiensis (43.7%) from Senegal. The trypanosome prevalence in the four species from Burkina Faso was lower, i.e. 39.6% in Glossina medicorum, 18.08%; in Glossina morsitans submorsitans, 16.8%; in Glossina tachinoides and 10.5% in Glossina palpalis gambiensis. The trypanosome prevalence in Glossina palpalis gambiensis was lowest in Mali (6.9%) and Guinea (2.2%). The prevalence of SGHV and Wolbachia was very low irrespective of location or tsetse species with an average of 1.7% for SGHV and 1.0% for Wolbachia. In some cases, mixed infections with different trypanosome species were detected. The highest prevalence of coinfection was Trypanosoma vivax and other Trypanosoma species (9.5%) followed by coinfection of T. congolense with other trypanosomes (7.5%). The prevalence of coinfection of T. vivax and T. congolense was (1.0%) and no mixed infection of trypanosomes, SGHV and Wolbachia was detected.

Conclusion

The results indicated a high rate of trypanosome infection in tsetse wild populations in West African countries but lower infection rate of both Wolbachia and SGHV. Double or triple mixed trypanosome infections were found. In addition, mixed trypanosome and SGHV infections existed however no mixed infections of trypanosome and/or SGHV with Wolbachia were found.

     

Role of TLR2, TLR4, and MyD88 in murine ozone-induced airway hyperresponsiveness and neutrophilia.

Exposure to air pollutants such as ozone (O(3)) induces airway hyperresponsiveness (AHR) and airway inflammation. Toll-like receptors (TLR) are first-line effector molecules in innate immunity to infections and signal via adapter proteins, including myeloid differentiation factor-88 (MyD88). We investigated the sensing of ozone by TLR2, TLR4, and MyD88. Ozone induced AHR in wild-type (WT) C57BL/6 mice, but AHR was absent in TLR2(-/-), TLR4(-/-), and MyD88(-/-) mice. Bronchoalveolar lavage neutrophilia induced by ozone was inhibited at 3 h but not at 24 h in TLR2(-/-) and TLR4(-/-) mice, while in MyD88(-/-) mice, this was inhibited at 24 h. We investigated the expression of inflammatory cytokines and TLR2, TLR4, and MyD88 in these mice. Ozone induced time-dependent increases in inflammatory gene expression of keratinocyte chemoattractant (KC) and IL-6 and of TLR2, TLR4, and MyD88 in WT mice. IL-6 and KC expression induced by ozone was inhibited in TLR2(-/-), TLR4(-/-), and MyD88(-/-) mice. Expression of MyD88 was increased in TLR2(-/-) and TLR4(-/-) mice, while induction of TLR2 or TLR4 was reduced in TLR2(-/-) and TLR4(-/-) mice, respectively. TLR2 and TLR4 mediate AHR induced by oxidative stress such as ozone, while the adapter protein MyD88, but not TLR2 or TLR4, is important in mediating ozone-induced neutrophilia. TLR2 and TLR4 may also be important in regulating the speed of neutrophilic response. Therefore, ozone may induce murine AHR and neutrophilic inflammation through the activation of the Toll-like receptor pathway that may sense noninfectious stimuli such as oxidative stress.     

Materials for a study in animal competition

The incidence of the sewage fly, Psychoda alternata Say, breeding almost free from other insect competitors in a bacteria bed at Huddersfield is examined. Its general seasonal trend is marked by periods of peak output explained on the theory that there are two successions of generations running persistently and alternating with one another. Such behaviour has previously been demonstrated for another sewage fly, Spaniotoma minima , and has been shown to be instituted by irregular temperatures in autumn and spring. In Psychoda alternata a special type of intraspecific competition is set-up in the warmer months when the cycles are rapid, for the larvae of one succession must start life in a bed just depleted of food by the other. Therefore large and small outbursts of the fly tend to alternate. The discharges of solids from the bed have a detailed periodicity corresponding to the alternations in the successions of the fly.