BACKGROUND : Tsetse flies (Diptera: Glossinidae) and tabanids (Diptera: Tabanidae) are haematophagous insects of
medical and veterinary importance due to their respective role in the biological and mechanical transmission of
trypanosomes. Few studies on the distribution and relative abundance of both families have been conducted in
Mozambique since the country’s independence. Despite Nicoadala, Mozambique, being a multiple trypanocidal drug
resistance hotspot no information regarding the distribution, seasonality or infection rates of fly-vectors are available.
This is, however, crucial to understanding the epidemiology of trypanosomosis and to refine vector management.
METHODS : For 365 days, 55 traps (20 NGU traps, 20 horizontal traps and 15 Epsilon traps) were deployed in three grazing
areas of Nicoadala District: Namitangurine (25 traps); Zalala (15 traps); and Botao (15 traps). Flies were collected
weekly and preserved in 70% ethanol. Identification using morphological keys was followed by molecular confirmation
using cytochrome c oxidase subunit 1 gene. Trap efficiency, species distribution and seasonal abundance were
also assessed. To determine trypanosome infection rates, DNA was extracted from the captured flies, and submitted
to 18S PCR-RFLP screening for the detection of Trypanosoma.
RESULTS : In total, 4379 tabanids (of 10 species) and 24 tsetse flies (of 3 species), were caught. NGU traps were more
effective in capturing both the Tabanidae and Glossinidae. Higher abundance and species diversity were observed in
Namitangurine followed by Zalala and Botao. Tabanid abundance was approximately double during the rainy season
compared to the dry season. Trypanosoma congolense and T. theileri were detected in the flies with overall infection
rates of 75% for tsetse flies and 13% for tabanids. Atylotus agrestis had the highest infection rate of the tabanid species.
The only pathogenic trypanosome detected was T. congolense.
CONCLUSIONS : Despite the low numbers of tsetse flies captured, it can be assumed that they are still the cyclical
vectors of trypanosomosis in the area. However, the high numbers of tabanids captured, associated to their demonstrated
capacity of transmitting trypanosomes mechanically, suggest an important role in the epidemiology of
trypanosomosis in the Nicoadala district. These results on the composition of tsetse and tabanid populations as well as the observed infection rates, should be considered when defining strategies to control the disease.
Additional file 1: Figure S1. An uncorrected p-distance data-display
network, using all characters recovered from SplitsTree using the Tabanidae
cox1 data. Bootstrap (bs) support calculated from 1000 replicates is
indicated for the various groupings. The double-digit numbers (intuitional
voucher numbers) on the tips of the network represent the sequences
from this study.
Additional file 2: Figure S2. An uncorrected p-distance data-display
network, using all characters recovered from SplitsTree using the Glossinidae
cox1 data. Bootstrap (bs) support calculated from 1000 replicates
is indicated for the various groupings. The double-digit numbers on the
tips of the network represent the sequences from this study. Red arrows
indicate the specimen sequences from this study.
Additional file 3: Table S1. Metadata for all specimens analysed.