Abiotic and biotic factors associated with the presence of Anopheles arabiensis immatures and their abundance in naturally occurring and man-made aquatic habitats

Table 1 Comparison of different group means (+ SEM) of environmental variables between aquatic habitats with and without Anopheles arabiensis larvae in Bras-Panon

	Mosquito larvae
Environmental variables	Present	Absent	p-value
Total number of habitats sampled	14	14	−
Flow (velocity in m/s))	Stagnant (0)	0.41 ± 1.4	=
Water body area (m2)	8.42 ± 7.2	5.81 ± 3.7	0.58**
Water depth (cm)	3.25 ± 1.1	3.51 ± 0.9	0.24**
Turbid/clear (%)	40%/60%	99.4%/0.6%	0.002*
Temperature (°C)	32.12 ± 3.9	31.93 ± 1.9	0.15**
pH	8.78 ± 1.26	8.61 ± 1.07	0.29**
% emergent vegetation	30%	45%	0.43*
% algae	45%	75%	0.05*
Number of macro-invertebrate species (diversity index)	12 (1.78)	10 (1.92)	0.014***
Number of grass species (diversity index)	11 (1.61)	9 (1.84)	0.001***

=: 30% of aquatic without An. arabiensis were slow moving while the remaining and those with larvae were stagnant. * Wald chi square test. ** GLM F-test. *** Wilcoxon test.
‘Positive habitat’ was defined as a water body which could contain at least one larva on any sampling visit, in contrast to ‘negative habitat’ which refers to habitat with no single larvae sighted from at least 5–10 dips (depending on size) on each occasion. These were selected among the commonly encountered aquatic habitats that were likely to hold water throughout the study period. The selection of aquatic habitats for sampling was done in a way as to reflect the diversity of water bodies present in individual study sites.

ISSN: 1756-3305