Seasonal Variation in Biting Rates of Simulium damnosum sensu lato, Vector of Onchocerca volvulus, in Two Sudanese Foci

Autor: Tong Chor M. Deran, Ehab A. M. Frah, Isam M. A. Zarroug, Tarig B. Higazi, Kamal Hashim, Abdallah M. Samy, Arwa Elaagip, Hanan A. Mohamed, Nabil Aziz, Wigdan A. ElMubarak
Rok vydání: 2016
Předmět:
Male
0301 basic medicine
Atmospheric Science
Veterinary medicine
Rain
Climate
lcsh:Medicine
Onchocerciasis
Geographical Locations
Sudan
0302 clinical medicine
Medicine and Health Sciences
Simuliidae
lcsh:Science
Multidisciplinary
Animal Behavior
Geography
Ecology
Temperature
030108 mycology & parasitology
Infectious Diseases
Helminth Infections
Female
Seasons
Research Article
Neglected Tropical Diseases
Infectious Disease Control
030231 tropical medicine
Animal Sexual Behavior
Biology
Insect bites and stings
Specimen Handling
03 medical and health sciences
Meteorology
Surface Water
Parasitic Diseases
medicine
Adults
Animals
Humans
Relative species abundance
Behavior
lcsh:R
Biology and Life Sciences
Insect Bites and Stings
Seasonality
Tropical Diseases
biology.organism_classification
medicine.disease
Onchocerca volvulus
Insect Vectors
Biting
Age Groups
Vector (epidemiology)
People and Places
Africa
Earth Sciences
Population Groupings
lcsh:Q
Hydrology
Zoology
Black fly
Zdroj: PLoS ONE, Vol 11, Iss 3, p e0150309 (2016)
PLoS ONE
ISSN: 1932-6203
DOI: 10.1371/journal.pone.0150309
Popis: Background The abundance of onchocerciasis vectors affects the epidemiology of disease in Sudan, therefore, studies of vector dynamics are crucial for onchocerciasis control/elimination programs. This study aims to compare the relative abundance, monthly biting-rates (MBR) and hourly-based distribution of onchocerciasis vectors in Abu-Hamed and Galabat foci. These seasonally-based factors can be used to structure vector control efforts to reduce fly-biting rates as a component of onchocerciasis elimination programs. Methods A cross-sectional study was conducted in four endemic villages in Abu-Hamed and Galabat foci during two non-consecutive years (2007–2008 and 2009–2010). Both adults and aquatic stages of the potential onchocerciasis vector Simulium damnosum sensu lato were collected following standard procedures during wet and dry seasons. Adult flies were collected using human landing capture for 5 days/month. The data was recorded on handheld data collection sheets to calculate the relative abundance, MBR, and hourly-based distribution associated with climatic factors. The data analysis was carried out using ANOVA and Spearman rank correlation tests. Results Data on vector surveillance revealed higher relative abundance of S. damnosum s.l. in Abu- Hamed (39,934 flies) than Galabat (8,202 flies). In Abu-Hamed, vector populations increased in January-April then declined in June-July until they disappeared in August-October. Highest black fly density and MBR were found in March 2007 (N = 9,444, MBR = 58,552.8 bites/person/month), and March 2010 (N = 2,603, MBR = 16,138.6 bites/person/month) while none of flies were collected in August-October (MBR = 0 bites/person/month). In Galabat, vectors increased in September-December, then decreased in February-June. The highest vector density and MBR were recorded in September 2007 (N = 1,138, MBR = 6,828 bites/person/month) and September 2010 (N = 1,163, MBR = 6,978 bites/person/month), whereas, none appeared in collection from April to June. There was a significant difference in mean monthly density of S. damnosum s.l. across the two foci in 2007–2008 (df = 3, F = 3.91, P = 0.011). Minimum temperature showed significant correlation with adult flies counts in four areas sampled; the adult counts were increased in Nady village (rs = 0.799) and were decreased in Kalasecal (rs = - 0.676), Gumaiza (rs = - 0.585), and Hilat Khateir (rs = - 0.496). Maximum temperature showed positive correlation with black fly counts only in Galabat focus. Precipitation was significantly correlated with adult flies counts in Nady village, Abu-Hamed, but no significance was found in the rest of the sampled villages in both foci. Hourly-based distribution of black flies showed a unimodal pattern in Abu-Hamed with one peak (10:00–18:00), while a bimodal pattern with two peaks (07:00–10:00) and (14:00–18:00) was exhibited in Galabat. Conclusion Transmission of onchocerciasis in both foci showed marked differences in seasonality, which may be attributed to ecology, microclimate and proximity of breeding sites to collection sites. The seasonal shifts between the two foci might be related to variations in climate zones. This information on black fly vector seasonality, ecology, distribution and biting activity has obvious implications in monitoring transmission levels to guide the national and regional onchocerciasis elimination programs in Sudan.
Databáze: OpenAIRE
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