Molecular identification of different trypanosome species and subspecies in tsetse flies of northern Nigeria.

BACKGROUND: Animal African Trypanosomiasis (AAT) is caused by several species of trypanosomes including Trypanosoma congolense, T. vivax, T. godfreyi, T. simiae and T. brucei. Two of the subspecies of T. brucei also cause Human African Trypanosomiasis. Although some of them can be mechanically transmitted by biting flies; these trypanosomes are all transmitted by tsetse flies which are the cyclical vectors of Trypanosoma congolense, T. godfreyi, T. simiae and T. brucei. We present here the first report assessing the prevalence of trypanosomes in tsetse flies in Nigeria using molecular tools. METHODS: 488 tsetse flies of three species, Glossina palpalis palpalis, G. tachinoides and G. morsitans submorsitans were collected from Wuya, Niger State and Yankari National Park, Bauchi State in 2012. Trypanosomes were detected and identified using an ITS1 PCR assay on DNA purified from the 'head plus proboscis' (H + P) and abdomen (ABD) parts of each fly. RESULTS: T. vivax and T. congolense Savannah were the major parasites detected. Trypanosomes prevalence was 7.1 % in G. p. palpalis, 11.9 % in G. tachinoides and 13.5 % in G. m. submorsitans. Prevalences of T. congolense Savannah ranged from 2.5 to 6.7 % and of T. vivax were approximately 4.5 %. Trypanosoma congolense Forest, T. godfreyi and T. simiae were also detected in the site of Yankari. The main biological and ecological determinants of trypanosome prevalence were the fly sex, with more trypanosomes found in females than males, and the site, with T. congolense subspp. being more abundant in Yankari than in Wuya. As expected, the trypanosome species diversity was higher in Yankari National Park than in the more agricultural site of Wuya where vertebrate host species diversity is lower. CONCLUSIONS: Our results show that T. congolense Savannah and T. vivax are the main species of parasite potentially causing AAT in the two study sites and that Yankari National Park is a potential reservoir of trypanosomes both in terms of parasite abundance and species diversity.

Entomological assessment of yellow fever-epidemic risk indices in Benue State, Nigeria, 2010-2011.

Yellow fever (YF) is a vector-borne disease affecting humans and non-human primates in tropical areas. In the past, there have been pockets of YF outbreaks in Nigeria that resulted in preventable deaths. Surveillance efforts towards avoiding another outbreak have been put in place with the aim of early detection and control. However, risk indices relating to the density of immature YF-mosquito vectors are given little consideration even though it is the first step in curbing a possible outbreak. Immature collections from 1538 houses in Ega, Oju, Otukpoicho and Otukpo in Benue State were carried out in 2010 and 2011. Risk indices such as house index (HI), container index (CI) and Breteau index (BI) were estimated. Molecular detection of YF was carried out on randomly selected Aedes larvae and pupae. Overall, 431,381 mosquitoes were collected in and around house premises. Thirteen species were identified: Ae. aegypti (Linneaus), Ae. africanus (Theobald), Ae. albopictus (Skuse), Ae. cumminsii (Theobald), Ae. luteocephalus (Newstead), Ae. simpsoni s.l. (Theobald), Ae. vittatus (Bigot), Anopheles gambiae Giles, An. nili (Theobald), Cx. nebulosus Theobald, Culex quinquefasciatus Say, Lutzia tigripes (Grandpre and Charmoy) and Toxorhynchites brevipalpis Theobald. The HI, CI and BI for Ae. aegypti were high in all the study locations, but low for Ae. lueteocephalus except in Ega. With 50 immature Aedes mosquitoes screened across locations, only Ae. aegypti from Ega were positive for YF. This study places Ega on a high alert of an impending YF outbreak. Thus, urgent steps to clear this area of potential mosquito sites are highly recommended.

Insecticidal activity of the medicinal plant, Alstonia boonei De Wild, against Sesamia calamistis Hampson.

The bioactivity of the aqueous extracts of the leaf and stem bark of the medicinal plant, Alstonia boonei De Wild (Apocyanaceae), against the pink stalk borer, Sesamia calamistis Hampson (Lepidoptera: Noctuidae) was studied in a laboratory bioassay. The extracts were incorporated into artificial diet at a rate of 0.0% (control), 1.0%, 2.5%, 5.0%, and 10.0% (w/w). Both extracts significantly (P<0.01) reduced larval survival and weight in a dose dependent manner. The concentrations that killed 50% of the larvae (LC(50)) for the stem bark extract were 2.8% and 2.1% at 10 and 20 DAI (days after introduction), respectively, while those for the leaves extract were 5.6% and 3.5%. The weights of the larvae also varied significantly (P<0.05) between the treatments in a dose dependent manner. We conclude that both leaf and stem bark extracts of A. boonei are toxic, used as growth inhibitors to S. calamistis larvae, and hold good promise for use as alternative crop protectants against S. calamistis.