Parasites and Vectors (2012) 5 (117) - Abundance and dynamics of ...

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Abebe Animut, Teshome Gebre-Michael, Meshesha Balkew and Bernt Lindtjørn (2012)
Abundance and dynamics of anopheline larvae in a highland malarious area of south-central Ethiopia
Parasites and Vectors 5 (117)
Abstract: Background
Malaria is a public health problem in Ethiopia, and increasingly so in highland areas, possibly because of global warming. This study describes the distribution, breeding habitat and monthly dynamics of anopheline larvae in Butajira, a highland area in south-central Ethiopia.
Methods
A study of the abundance and dynamics of Anopheles larvae was undertaken at different sites and altitudes in Butajira from July 2008 to June 2010. The sites included Hobe (1817 m.a.s.l), Dirama (1995m.a.s.l.) and Wurib (2196m.a.s.l.). Potential anopheline larval habitats were surveyed once per month in each village. The recorded characteristics of the habitats included habitat type, pH, surface debris, emergent plants, algae, substrate, turbidity, temperature, length, width, depth, distance to the nearest house and anophelines. The Spearman correlation coefficient and Mann-Whitney U test were used to calculate the degree of association between the density of anopheline species and key environmental factors.
Results
Among the different types of habitat surveyed, the Odamo, Akamuja and Assas streams and Beko swamp were positive for anopheline larvae. A total of 3,957 third and fourth instar larvae were collected from the three localities, and they represented ten species of anophelines. These were: Anopheles cinereus (32.5%), An. arabiensis (31.4%), An. chrysti (23%), An. demeilloni (12.2%), An. pretoriensis (0.6%), An. azaniae (0.1%), An. rufipes(0.1%), An. sergentii (0.06%), An. garnhami (0.06%) and An. pharoensis (0.03%). The density of anopheline larvae was highest during the dry months. An. arabiensis was widely distributed, and its density decreased from the lowest elevation in Hobe to the highest in Wurib. The density of An. arabiensis larvae was correlated positively with larval habitat temperature (r = 0.33, p < 0.05) and negatively with depth of larval habitat (r = −0.56, p < 0.05).
Conclusion
Ten species of anophelines were identified, including two known vectors of malaria (An. arabiensis and An. pharoensis), along streams in Butajira. Larvae of An. arabiensis were found in streams at 2200m.a.s.l. This possible expansion of the malaria vector to highland areas indicates an increasing risk of malaria because a large proportion of the Ethiopian population live above this altitude.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
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Database assignments for author(s): Abebe Animut, Teshome Gebre-Michael

Research topic(s) for pests/diseases/weeds:
surveys/sampling/distribution
environment - cropping system/rotation


Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.


Anopheles arabiensis Ethiopia
Anopheles pharoensis Ethiopia
Anopheles azaniae Ethiopia
Anopheles pretoriensis Ethiopia
Anopheles demeilloni Ethiopia
Anopheles cinereus Ethiopia
Anopheles sergentii Ethiopia
Anopheles rufipes Ethiopia
Anopheles garnhami Ethiopia
Anopheles christyi Ethiopia