Abstract
.Following the halt of mass drug administration (MDA) for lymphatic filariasis (LF), the WHO recommends at least 4 years of post-treatment surveillance (PTS) to confirm that transmission recrudescence or importation does not occur. The primary means of evaluation during PTS is repeated transmission assessment surveys (TASs) conducted at 2- to 3-year intervals after TAS-1 stop-MDA surveys. This study reports the results of TAS-2 and TAS-3 surveys in Plateau and Nasarawa states (pop. 6.9 million) of Nigeria divided into a minimum of seven evaluation units (EUs) per TAS. A total of 26,536 first- and second-year primary school children (approximately 6–7 years old) were tested for circulating filarial antigen (CFA) between 2014 and 2017. Of 12,313 children tested in TAS-2 surveys, only five (0.04%) were CFA positive, with no more than two positive samples from any one EU, which was below the critical value of 20 per EU. Of 14,240 children tested in TAS-3 surveys, none (0%) were CFA positive. These results indicate that LF transmission remains below sustainable transmission levels and suggest that elimination of transmission has been achieved in Plateau and Nasarawa, Nigeria.
Highlights
Lymphatic filariasis (LF) is a mosquito-transmitted parasitic disease caused by infection with Wuchereria bancrofti, Brugia malayi, or Brugia timori
Since the launch of the Global Program to Eliminate LF (GPELF) in 2000, approximately 7.1 billion treatments have been distributed resulting in the elimination of LF as a public health problem in 11 countries through 2017.13 progress has been slowest in Africa, where only two African countries to date—Togo and Egypt—have met this milestone.[13]
Results from this study indicate that two formerly endemic Nigerian states, Plateau and Nasarawa, have met the WHO epidemiological requirements for post-treatment surveillance (PTS)—that is, < 2% antigen prevalence in children in areas where W. bancrofti is transmitted by Anopheles or Culex mosquitoes—and suggest that LF transmission has been eliminated in the area
Summary
Lymphatic filariasis (LF) is a mosquito-transmitted parasitic disease caused by infection with Wuchereria bancrofti, Brugia malayi, or Brugia timori. It is a leading cause of permanent and long-term disability due to its disfiguring and debilitating manifestations that include lymphedema, elephantiasis, male scrotal swelling (hydrocele), and acute febrile episodes of adenolymphangitis.[1] These conditions result from chronic dysfunction caused by adult worms inhabiting the lymphatic vessels. Gravid females produce millions of infective microfilariae (mf) that circulate in the lymphatic and blood systems. Annual mass drug administration (MDA) at sufficient population coverage (3 65%) is predicted to interrupt LF transmission in a population in 4–6 years—the estimated lifespan of adult worms.[3]
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