Abstract
Background
The impact of large scale Mass Drug Adminstration (MDA) of ivermectin on active onchocerciasis transmission by Simulium damnosum, which transmits the parasite O. volvulus is of great importance for onchocerciasis control programmes. We investigated in the Mbam river system area, the impact of MDA of ivermectin on entomological indices and also verify if there are river system factors that could have favoured the transmission of onchocerciasis in this area and contribute to the persistence of disease. We compared three independent techniques to detect Onchocerca larvae in blackflies and also analyzed the river system within 9 months post-MDA of ivermectin.
Method
Simulium flies were captured before and after 1, 3, 6 and 9months of ivermectin-MDA. The biting rate was determined and 41% of the flies dissected while the rest were grouped into pools of 100 flies for DNA extraction. The extracted DNA was then subjected to O-150 LAMP and real-time PCR for the detection of infection by Onchocerca species using pool screening. The river system was analysed and the water discharge compared between rainy and dry seasons.
Principal findings
We used human landing collection method (previously called human bait) to collect 22,274 adult female Simulium flies from Mbam River System. Of this number, 9,134 were dissected while 129 pools constituted for molecular screening. Overall biting and parous rates of 1113 flies/man/day and 24.7%, respectively, were observed. All diagnostic techniques detected similar rates of O. volvulus infection (P = 0.9252) and infectivity (P = 0.4825) at all monitoring time points. Onchocerca ochengi larvae were only detected in 2 of the 129 pools. Analysis of the river drainage revealed two hydroelectric dams constructed on the tributaries of the Mbam river were the key contributing factor to the high-water discharge during both rainy and dry seasons.
Conclusion
Results from fly dissection (Microscopy), real-time PCR and LAMP revealed the same trends pre- and post-MDA. The infection rate with animal Onchocerca sp was exceptionally low. The dense river system generate important breeding sites that govern the abundance of Simulium during both dry and rainy seasons.
Funder
DFG
UNICEF/UNDP/World Bank/SHO
Publisher
Public Library of Science (PLoS)
Subject
Infectious Diseases,Public Health, Environmental and Occupational Health
Reference47 articles.
1. The development of Onchocerca volvulus in Simolium damnosum;DB Blacklock;Ann Trop Med Parasitol,1926
2. River blindness: an old disease on the brink of elimination and control;KL Winthrop;J Glob Infect Dis,2011
3. WHO (2019) Onchocerciasis. [Online]. https://www.who.int/en/news-room/fact-sheets/detail/onchocerciasis. [Accessed 22 October 2020].
4. WHO (2020) Uniting to Combat Neglected Tropical Diseases. River blindness (Onchocerciasis). 2020 WHO roadmap target: Elimination. https://unitingtocombatntds.org/ntds/onchocerciasis/. (Accessed April 02 2020).
5. An appraisal of the neglected tropical diseases control program in Cameroon: the case of the national program against onchocerciasis;T Njim;BMC Public Health,2017
Cited by
12 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献