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Malar J. 2017 Jun 6;16(1):239. doi: 10.1186/s12936-017-1885-x.

Ivermectin-treated cattle reduces blood digestion, egg production and survival of a free-living population of Anopheles arabiensis under semi-field condition in south-eastern Tanzania.

Author information

1
Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, P.O.BOX 53, Ifakara, Morogoro, United Republic of Tanzania. ilyimo@ihi.or.tz.
2
Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, P.O.BOX 53, Ifakara, Morogoro, United Republic of Tanzania.
3
Pest Management Centre, Sokoine University of Agriculture, Morogoro, Tanzania.
4
School of Public Health, University of the Witwatersrand, Parktown, Republic of South Africa.

Abstract

BACKGROUND:

Anopheles arabiensis feed on cattle and contributes to residual transmission of malaria in areas with high coverage of long-lasting insecticide-treated nets and indoor residual spraying in East Africa. This study aimed to evaluate the effects of ivermectin-treated cattle as a complementary vector control tool against population of An. arabiensis under the semi-field conditions in south-eastern Tanzania.

METHODS:

The free-living population of An. arabiensis was allowed to forage on untreated or ivermectin-treated cattle in alternating nights within the semi-field system in south-eastern Tanzania. Fresh blood fed mosquitoes were collected in the morning using mouth aspirators and assessed for their blood meal digestion, egg production, and survivorship. The residual activity of ivermectin-treated cattle was also determined by exposing mosquitoes to the same treatments after every 2 days until day 21 post-treatments. These experiments were replicated 3 times using different individual cattle.

RESULTS:

Overall, the ivermectin-treated cattle reduced blood meal digestion in the stomach of An. arabiensis, and their subsequent egg production and survival over time. The ivermectin-treated cattle halved blood meal digestion in mosquitoes, but reduced their egg production for up to 15 days. The ivermectin-treated cattle reduced the survival, and median survival times (1-3 days) of An. arabiensis than control cattle. The daily mortality rates of mosquitoes fed on ivermectin-treated cattle increased by five-fold relative to controls in the first week, and it gradually declined up to 21 days after treatment.

CONCLUSION:

This study demonstrates that long-lasting effects of ivermectin-treated cattle on egg production and survival of An. arabiensis may sustainably suppress their vector density, and reduce residual transmission of malaria. This study suggests that ivermectin-treated non-lactating cattle (i.e. calves, heifers and bulls) could be suitable option for large-scale malaria vector control without limiting consumption of milk and meat by communities in rural settings. Furthermore, simulation models are underway to predict the impact of ivermectin-treated cattle alone, or in combination with LLIN/IRS, the frequency of treatment, and their coverage required to significantly suppress population of An. arabiensis and reduce residual transmission of malaria.

KEYWORDS:

Anopheles arabiensis; Blood-digestion; Cattle; Egg-production; Exophagy; Haematin; Ivermectin; Residual-transmission; Survival; Vector–control; Zoophagy

PMID:
28587669
PMCID:
PMC5461717
DOI:
10.1186/s12936-017-1885-x
[Indexed for MEDLINE]
Free PMC Article

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