Predicted distribution and movement of Glossina palpalis palpalis (Diptera: Glossinidae) in the wet and dry seasons in the Kogo trypanosomiasis focus (Equatorial Guinea).

The aim of this study was to predict the distribution and movement of populations of the tsetse fly, Glossina palpalis palpalis (Diptera: Glossinidae), in the wet and dry seasons and to analyze the impact of the use of mono-pyramidal traps on fly populations in the Kogo focus in 2004 and 2005. Three Glossina species are present in Kogo: Glossina palpalis palpalis, major HAT vector in West-Central Africa, Glossina caliginea, and Glossina tabaniformis. The apparent density (AD) of G. p. palpalis clearly fell from 1.23 tsetse/trap/day in July 2004 to 0.27 in December 2005. A significant reduction in the mean AD for this species was noted between seasons and years. The diversity of Glossina species was relatively low at all the sampling points; G. p. palpalis clearly predominated over the other species and significantly dropped as a consequence of control activities. The predictive models generated for the seasonal AD showed notable differences not only in the density but in the distribution of the G. p. palpalis population between the rainy and dry season. The mono-pyramidal traps have proven to be an effective instrument for reducing the density of the tsetse fly populations, although given that the Kogo trypanosomiasis focus extends from the southern Equatorial Guinea to northern Gabon, interventions need to be planned on a larger scale, involving both countries, to guarantee the long-term success of control

Map of Luba focus and distribution of tsetse fly captures over the villages.

<p>Map of Luba focus and distribution of tsetse fly captures over the villages.</p

Distribution of animal sampling and infection amongst villages.

<p>Although three sheep were censed none of them could be sampled. In Musola, Rilaja, Bombe, Moeri and Patio Mora, no animals were present.</p

Revealed results of PCR in 2% agarose gel stained with ethidium bromide under UV.

<p><i>Above:</i> Samples from sixteen tsetse flies submitted to PCR using GmTub primers as DNA quality control. Expected band size ∼380 bp. <i>Middle:</i> Molecular diagnosis of samples from fifteen tsetse flies for <i>T. b. gambiense</i>. First sample corresponds to the one positive tsetse fly. The band at right is the positive control. Expected band size 270 bp. <i>Below:</i> Detection of <i>T. brucei</i> s.l. in animal samples. 5–8 and 11 are positives, 12 is the positive control. Expected band size 177 bp.</p

Distribution of tsetse fly captures and infection amongst villages.

<p>No flies were trapped in Moeri or Patio Mora.</p><p>*AD = Apparent density calculated as number of flies/trap/day.</p><p>**Boloco belongs to Fortuny village but a set of five traps were located there due to its relative geographical distance.</p

Screening of Trypanosoma brucei gambiense in domestic livestock and tsetse flies from an insular endemic focus (Luba, Equatorial Guinea).

BACKGROUND: Sleeping sickness is spread over 36 Sub-Saharan African countries. In West and Central Africa, the disease is caused by Trypanosoma brucei gambiense, which produces a chronic clinical manifestation. The Luba focus (Bioko Island, Equatorial Guinea) has not reported autochthonous sleeping sickness cases since 1995, but given the complexity of the epidemiological cycle, the elimination of the parasite in the environment is difficult to categorically ensure. METHODOLOGY/PRINCIPAL FINDINGS: The aim of this work is to assess, by a molecular approach (Polymerase Chain Reaction, PCR), the possible permanence of T. b. gambiense in the vector (Glossina spp.) and domestic fauna in order to improve our understanding of the epidemiological situation of the disease in an isolated focus considered to be under control. The results obtained show the absence of the parasite in peridomestic livestock but its presence, although at very low rate, in the vector. On the other hand, interesting entomological data highlight that an elevated concentration of tsetse flies was observed in two out of the ten villages considered to be in the focus. CONCLUSIONS: These findings demonstrate that even in conditions of apparent control, a complete parasite clearance is difficult to achieve. Further investigations must be focused on animal reservoirs which could allow the parasites to persist without leading to human cases. In Luba, where domestic livestock are scarcer than other foci in mainland Equatorial Guinea, the epidemiological significance of wild fauna should be assessed to establish their role in the maintenance of the infection