Malaria prevalence pattern observed in the highland fringe of Butajira, Southern Ethiopia: A longitudinal study from parasitological and entomological survey

BACKGROUND: In Ethiopia, information regarding highland malaria transmission is scarce, and no report has been presented from Butajira highland so far whether the appearance of malaria in the area was due to endemicity or due to highland malaria transmission. Thus this study aimed to determine the presence and magnitude of malaria transmission in Butajira. METHODS: For parasitological survey, longitudinal study was conducted from October to December 2006. The entomological surveys were done from October to December 2006 and continued from April to May 2007. Both parasitological and entomological surveys were done using standard procedures. RESULTS: The parasitological result in all the survey months (October-December) showed an overall detection rate of 4.4% (48/1082) (CI 95%; 3.2-5.7%) malaria parasite. Among infected individuals, 32 (3.0%) of the infection was due to Plasmodium vivax and the rest 16 (1.5%) were due to Plasmodium falciparum. The highest prevalence 39(3.6%) of the parasite was observed in age groups of above 15 years old. Among the total tested, 25(2.3%) of males and 23(2.1%) of females had malaria infection. Among tested individuals, 38(5.3%) and 10 (2.7%) of infection was occurred in Misrak-Meskan (2100 m a.s.l) and Mirab-Meskan (2280 m a.s.l), respectively which was statistically significant (X(2 )= 3.72, P < 0.05). Although the prevalence pattern of Plasmodium species declined from October to December, the trend was non-significant (X(2 )for trend = 0.49, P > 0.05). The entomological survey showed a collection of 602 larvae and 80 adult Anopheles. Anopheles christyi was the dominant species both in the first (45.3%) and in the second (35.4%) surveys; where as, Anopheles gambiae sensu lato comprised 4.7% and 14.6%, in the first and second surveys, respectively. Anopheles gambiae s.l comprises 55% of the adult collection, and both species were collected more from outdoors (57.5%). The number of An. christyi was higher in Mirab-Meskan (58. 3%) than Misrak-Meskan (41.7%) (P < 0.05). CONCLUSION: Malaria parasite and its vectors were found to be common during transmission periods in the highland fringes of Butajira. Thus, health education about the risk of malaria and its control programme in the area must be given adequate attention to minimize potential epidemics. In addition, the current study should be complemented from sero-epidemiological, prospective longitudinal and retrospective studies along with metrological and ecological factors, and socio-demographic data before concluding in favour of highland malaria transmission in the area. In light of its abundance, which coincided with the malaria transmission seasons, the possible role of An. christyi as a secondary vector in the highlands must be further investigated by including blood meal sources detection.