Enhancing acute flaccid paralysis surveillance system towards polio eradication: reverse cold chain monitoring in Nigeria, 2017 to 2019.

Introduction: Highly sensitive acute flaccid paralysis (AFP) surveillance is critical for detection of poliovirus circulation and documentation for polio-free certification. The reverse cold chain (RCC) is a system designed to maintain stool specimens in appropriate temperature for effective detection of poliovirus in the laboratory. We monitored the RCC of AFP surveillance in Nigeria to determine its effectiveness in maintaining viability of enterovirus. Methods: A descriptive cross-sectional study was conducted from November 2017 to December 2019. We included AFP cases from 151 Local Government Areas and monitored RCC of paired stool specimens from collection to arrival at laboratories. The national guideline recommends RCC temperature of +2 to +8°C and a non-polio enterovirus (NPENT) detection rate of ≥10%. We analyzed data with Epi Info 7, and presented results as frequencies and proportions, using Chi-square statistic to test for difference in enterovirus isolation. Results: Of the 1,042 tracked paired stool specimens, 1,038(99.6%) arrived at the laboratory within 72 hours of collection of second specimen, 824(79.1%) were maintained within recommended temperature range, and 271(26%) yielded enteroviruses: 200(73.8%) NPENT, 66(24.4%) Sabin, 3(1.1%) vaccine derived poliovirus type 2 and 2(0.7%) mixture of Sabin and NPENT. The NPENT and Sabin rates were 19.2% and 6.7% respectively. Twenty-five percent of 824 specimens maintained within recommended temperature range, compared with 29.8% of 218 specimens with temperature excursion yielded enteroviruses (P=0.175). Conclusion: the RCC of AFP surveillance system in the study area was optimal and effective in maintaining the viability of enteroviruses. It was unlikely that poliovirus transmission was missed during the intervention.

Influence of Meteorological Variables on Diversity and Abundance of Mosquito Vectors in Two Livestock Farms in Ibadan, Nigeria: Public Health Implications.

This study was undertaken to determine mosquito vector diversity and abundance in two livestock farms with previous history of arboviral activities in Ibadan, southwestern Nigeria. The influence of weather on mosquito populations was also studied. Adult mosquitoes were collected weekly in two proximate University of Ibadan livestock farms from March 2015 to February 2016 using CO2 baited CDC light trap and human landing collection methods. Mosquitoes were identified to species using morphological keys. Relationships and interaction of temperature, relative humidity, rainfall patterns and mosquito abundance were analysed using GENSTAT 4th edition. Among 6,195 adult mosquitoes collected, 16 species belonging to 5 genera were morphologically identified. Culex quinquefasciatus constituted the most abundant mosquito, representing 46.49% of all mosquitoes encountered. High abundance in mosquito population was noted in periods succeeding months with heavy rainfall, this is when arbovirus transmission risk is highest. A positive correlation was observed between relative humidity and abundance of Mansonia mosquitoes. This study shows the effect of weather on natural populations of mosquito vectors. The diverse mosquito species capable of transmitting arboviruses from animal reservoirs to human and animals in livestock farms and its environment in Ibadan, Nigeria was also revealed. There is need for intensive vector control strategies targeted at reducing mosquito populations and ultimately prevention of disease outbreaks.