Sero-prevalence of Human Onchocerciasis and Lymphatic Filariasis in Low-Endemic communities of Ogun State, Nigeria

This study reports the status of onchocerciasis and lymphatic filariasis (LF) in communities with low endemicity in Ogun-State, Nigeria. The Ov16/Wb123 biplex Rapid Diagnostic Test was used to screen 1,836 participants aged 5 years and above from 8 Local Government Areas (LGAs) from October to December, 2016. Skin snips and night blood were also used for microscopic detection of microfilariae (MF). A cumulative seroprevalence of 9.4% and 0.42% was recorded for onchocerciasis and LF respectively with a co-infection rate of 0.4%. Among the LGAs screened, Ijebu North-East recorded the highest seroprevalence of onchocerciasis (26.4%) and LF (0.9%) while Remo North, Sagamu and Obafemi-Owode LGAs recorded low prevalences ranging from 0.7 - 2.7% for both diseases. No positive result of MF was observed in all the communities screened, even in Ijebu North-East where seroprevalence was high, suggesting historic exposure to onchocerciasis and LF infection which may have occurred over time due to human migration during farming and fishing seasons. Extension of ongoing mass treatment in endemic LGAs is recommended for Ijebu North-East to ensure inclusion in the drive towards the elimination of the diseases in Ogun State.

Genetic Diversity and Emerging Zoonotic Onchocerca Species in Human Populations in Taraba State, Nigeria

Background: A better understanding of parasite population genetic processes in specific biogeography is needed to support onchocerciasis elimination goals. The genetic diversity of Onchocerca microfilariae was explored by amplifying a fragment of the 16S rRNA gene in the endemic area in Taraba State, Nigeria, Methods: Eight (8) communities were selected including six onchocerciasis endemic communities with records of ivermectin treatment having been annually distributed for 10 to 16 years, and two non-onchocerciasis endemic areas. The participants were 211 from endemic and 110 from non-endemic areas as control. Skin snips were taken from consenting participants by convenience sampling methods using a sterile sclera punch, from males and females residing within the communities for ten years and above or since birth, microfilaria and residual skin snips were preserved in RNALater® in a 1.5 ml micro-centrifuge tube. DNA was extracted from microfilariae recovered and from those in residual skin snip specimens. Polymerase Chain Reaction (PCR) amplification using specific primers for 16S genes was done to detect the identity of Onchocerca species. The amplified products were sequenced and analyzed for species identity. Results: Multiple sequence alignment and phylogenetic analysis results showed distinct diversity of two sample sequences (G49_O.v. Gashaka and Y02_O.v. Yorro) from other samples from the study area and other regions, indicating emergence of a new polymorphic strain of O. volvulus. Report of a preliminary case of emerging zoonosis of O. ochengi infection in human (skin snips) sample (O. ochengi G44) in this study. Conclusions: It is clear there is genetic diversity of Onchocerca species and emerging zoonosis in the study site. We suggest further investigation on the extent and potentials of emerging zoonotic onchocerciasis by O. ochengi, in the light of cattle, Simulium vectors, environmental and humans overlap in the study area.

Effect of Ivermectin Treatment on the Frequency of Seizures in Persons with Epilepsy Infected with Onchocerca volvulus

A clinical trial performed in the Democratic Republic of Congo (DRC), among persons with epilepsy (PWE) infected with Onchocerca volvulus treated with anti-seizure medication suggested that ivermectin reduces the seizure frequency. We assessed the effect of ivermectin treatment on seizure frequency in PWE with and without anti-seizure medication in three onchocerciasis endemic areas (Maridi, South Sudan; Aketi, DRC; and Mahenge, Tanzania). Pre- and 3–5 months post-ivermectin microfilariae densities in skin snips and seizure frequency were assessed. After ivermectin, the median (IQR) percentage reduction in seizure frequency in the study sites ranged from 73.4% (26.0–90.0) to 100% (50.0–100.0). A negative binomial mixed model showed that ivermectin significantly reduced the seizure frequency, with a larger decrease in PWE with a high baseline seizure frequency. Mediation analysis showed that ivermectin reduced the seizure frequencies indirectly through reduction in microfilariae densities but also that ivermectin may have a direct anti-seizure effect. However, given the short half-life of ivermectin and the fact that ivermectin does not penetrate the healthy brain, such a direct anti-seizure effect is unlikely. A randomized controlled trial assessing the ivermectin effect in people infected with O. volvulus who are also PWE on a stable anti-seizure regimen may be needed to clarify the causal relationship between ivermectin and seizure frequency.

Ivermectin Treatment Response in Two Rural Villages with a High Prevalence of Onchocerciasis and Epilepsy, Mahenge Tanzania

Background: Despite 20 years of ivermectin mass distribution in the Mahenge area, Tanzania, the prevalence of onchocerciasis and epilepsy has remained high in rural villages. We investigated the efficacy of ivermectin in reducing Onchocerca volvulus microfilariae and predictors for parasitic load following ivermectin treatment in persons with and without epilepsy in two rural villages.Methods: Between April and September 2019, 50 persons with epilepsy (PWE) and 160 randomly selected persons without epilepsy (PWOE) from Msogezi and Mdindo villages participated in a follow-up study. Skin snips were obtained pre- (baseline) and three months post-ivermectin treatment.Results: The overall prevalence of O. volvulus positive skin snips at baseline was 49% (103/210), with no significant difference between PWE (58.0%) and PWOE (46.3%); p=0.197. The overall median microfilarial density was significantly higher at baseline (0.0 mf/mg, IQR: 0.0-1.7) than three month post-ivermectin treatment (0.0 mf/mg, IQR: 0.0-0.0), p<0.001. Three months after ivermectin, the microfilarial density had decreased by ≥80% in 54 (81.8%, 95%CI: 72.3-91.4) of the 66 individuals with positive skin snips at baseline. High microfilarial density at baseline was the only significant predictor associated with higher microfilarial density in the post-ivermectin skin snips. Conclusion: Our study reports a satisfactory decrease in microfilarial density following ivermectin treatment in most individuals. This suggests that optimizing ivermectin coverage will address the ongoing onchocerciasis transmission in Mahenge.

Comparison of Diagnostic Tests for Onchocerca volvulus in the Democratic Republic of Congo

Onchocerciasis is diagnosed by detecting microfilariae in skin snips or by detecting OV16 IgG4 antibodies in blood by either enzyme linked immunosorbent assay (ELISA) or a rapid diagnostic test (RDT). Here, we compare the sensitivity and specificity of these three tests in persons with epilepsy living in an onchocerciasis endemic region in the Democratic Republic of Congo. Skin snips and blood samples were collected from 285 individuals for onchocerciasis diagnosis. Three tests were performed: the OV16 RDT (SD Bioline) and the OV16 ELISA both on serum samples, and microscopic detection of microfilariae in skin snips. The sensitivity and specificity of each test was calculated with the combined other tests as a reference. Microfilariae were present in 105 (36.8%) individuals, with a median of 18.5 (6.5–72.0) microfilariae/skin snip. The OV16 RDT and OV16 ELISA were positive in, respectively, 112 (39.3%) and 143 (50.2%) individuals. The OV16 ELISA had the highest sensitivity among the three tests (83%), followed by the OV16 RDT (74.8%) and the skin snip (71.4%). The OV16 RDT had a higher specificity (98.6%) compared to the OV16 ELISA (84.8%). Our study confirms the need to develop more sensitive tests to ensure the accurate detection of ongoing transmission before stopping elimination efforts.

Loa loa Microfilariae in Skin Snips: Consequences for Onchocerciasis Monitoring and Evaluation in L. loa–Endemic Areas

The specificity of skin snips for onchocerciasis diagnoses is considered to be almost 100%. Our molecular methods revealed that microfilariae emerging from skin snips collected from highly microfilaremic Loa loa–infected individuals were largely misidentified as Onchocerca volvulus. This has important implications for onchocerciasis diagnostic testing in Loa-endemic areas.

Seroprevalence of onchocerciasis in Ogun State, Nigeria after ten years of mass drug administration with ivermectin

Background: This serological study conducted between March and July 2015 investigated the status of onchocerciasis in Ogun State, Nigeria after a decade of mass drug administration (MDA) with ivermectin. Baseline information from the rapid epidemiological mapping of onchocerciasis (REMO) prior to MDA had indicated that Ogun State was meso-endemic to onchocerciasis. Following years of treatment with ivermectin, it has become important to investigate the current status of the disease using more sensitive diagnostic methods.Methods: The study was conducted in 32 communities in eight onchocerciasis-endemic local government areas (LGAs). Using the Ov16 rapid diagnostic test (Ov16 RDT), finger-prick whole blood was obtained from 3 895 consented participants from age five and above. Skin snips were obtained from a subset of 481 corresponding participants as the majority of community members did not consent to skin snipping.Results: Study revealed a cumulative seroprevalence of 9.3% (CI 9.29–9.31%) by RDT and 17.3% (CI 16.73–18.34%) microfilaridermia prevalence by the skin snip subset. Seroprevalence among children between the ages of five and nine was 2.9% (CI 1.74–3.53%) across all LGAs. A community microfilaria load (CMFL) between 0 and 1.21 MF/skin snip was recorded in the different communities studied. Among the studied LGAs, children in Odeda LGA recorded the highest seroprevalence by RDT (14.9%) followed by Abeokuta North (5.1%), Abeokuta South (4.8%) and Imeko-Afon (0.6%), while Ewekoro, Ifo, Obafemi-Owode and Yewa North LGAs recorded zero prevalence.Conclusion: It appears that the elimination of onchocerciasis in some LGAs is possible considering the lack of new infection among children and the hypo-endemicity among the adult population. However, the microfilaria prevalence observed among adults is of concern as it may imply that mass treatment has not been effective. Increased therapeutic coverage is advised to fully maximise the potential of ivermectin treatment to achieve the disease elimination.

Sarcoptes scabiei (Acari: Sarcoptidae) infestation in rabbits (Oryctolagus cuniculus): A case study

Sarcoptic mange was suspected in three of five European albino rabbits (Oryctolagus cuniculus) kept for experimental purposes. Gross examination revealed multifocal areas of alopecia around the eyes, nostrils and lips. Skin snips were processed using PCR for the molecular identification of the suspected mites. Histopathology of the skin snips showed erupted epidermis and stratum corneum with an infiltration of inflammatory cells. Skin scraping examination revealed the presence of adult mites as well as eggs. Microscopic taxonomy identified the adult mites as Sarcoptes (S.) scabiei (Acari: Sarcoptidae). The results of PCR indicated a 311 bp band from all the three cases, which confirmed the S. scabiei infestation in rabbits. Sarcoptes scabiei may be a public health concernthrough direct transmission from rabbits infested with S. scabiei through handling. To the best of our knowledge, this is the first report of S. scabiei infection in rabbits from Pakistan.