Neutralization of the lethality of the venom of Dendroaspis polylepis (black mamba) in mice by two polyvalent antivenoms used in Kenyan hospitals: Results of a 2009–2011 study

Generation of chicken-based IgY polyclonal antibodies against Dendroaspis polylepis and preclinical evaluation of envenomation-neutralizing efficacy vis-à-vis selected commercial antivenoms

The Black mamba, D. polylepis, is one of the many venomous snakes found in Kenya, and known to account for some snakebite incidents. The Kenyan Ministry of Health data reveals annual 15,000 snakebites occurrences. Also, 1 in 15 people in Kenya gets bitten by a snake, and tragically, 1 in 147 of these individuals die of snakebite yearly. Traditionally, antivenoms for treatment are produced from horse or sheep but have complicated and expensive production issues. Alternative production approaches, such as using IgY antibodies derived from chicken egg yolks, may overcome disadvantages with traditional antivenom manufacturing techniques. In this current study, D. polylepis specific IgY polyclonal antibodies were purified from the egg yolks of chickens immunized with D. polylepis venom. These antibodies were subsequently assessed for their in-vivo neutralizing capacity vis-à-vis commercial antivenoms, PANAF-Premium and VINS. The IgY antibodies were purified by ammonium sulfate precipitation and affinity-chromatography, with quality and specificity determined by SDS-PAGE and ELISA. The LD50 of D. polylepis was found to be 0.54 mg/kg in chicks, and 0.34 mg/kg in mice, respectively. Pool of extracted IgY yielded 2.8 mg/mL concentration. Purified IgY under non-reducing and reducing conditions on SDS-PAGE exhibited a single-protein band of about 183 kDa and two bands (67 kDa and 25 kDa), respectively. The minimum-edematogenic dose was 0.05 μg. Anti-D. polylepis IgY antibodies and two antivenoms demonstrated the capacity to neutralize the toxic activities of D. polylepis venom. This study confirms a successful IgY generation against Black mamba venom for the first time, and observed toxic effects of the venom as well as neutralizing capacity of antivenoms.

Intrageneric cross-reactivity of monospecific rabbit antisera against venoms of mamba (Elapidae: Dendroaspis spp.) snakes

Snakebite envenomation is a neglected tropical disease posing a high toll of mortality and morbidity in sub-Saharan Africa. Polyspecific antivenoms of broad effectiveness and specially designed for this region require a detailed understanding of the immunological features of the mamba snake (Dendroaspis spp.) venoms for the selection of the most appropriate antigen combination to produce antivenoms of wide neutralizing scope. Monospecific antisera were generated in rabbits against the venoms of the four species of mambas. The toxic effects of the immunization scheme in the animals were evaluated, antibody titers were estimated using immunochemical assays, and neutralization of lethal activity was assessed. By the end of the immunization schedule, rabbits showed normal values of the majority of hematological parameters tested. No muscle tissue damage was noticed, and no alterations in most serum chemical parameters were observed. Immunological analyses revealed a variable extent of cross-reactivity of the monospecific antisera against the heterologous venoms. The venoms of D. jamesoni and D. viridis generated the antisera with broader cross-reactivity by immunochemical parameters. The venoms of D. polylepis and D. viridis generated the antisera with better cross-neutralization of lethality, although the neutralizing ability of all antisera was lower than 0.16 mg venom/mL antiserum against either homologous or heterologous venoms. These experimental results must be scaled to large animal models used in antivenom manufacture at industrial level to assess whether these predictions are reproducible.

Traditional remedies and other characteristics among human snakebite survivors in Baringo county, Kenya, 2010-2020: a case series

BACKGROUND

Seeking traditional remedies following snakebites leads to avoidable deaths in rural settings in developing countries.

METHODS

In this case series study, we identified and recruited 169 snakebite survivors in Baringo county, a hard-to-reach region in northwestern Kenya, who experienced snakebites from 2010 to 2020 using a snowballing technique. We explored associations between traditional and hospital care in managing snakebites and other characteristics. χ2 tests assessed these categorical differences.

RESULTS

Fifty-four (33%) of the survivors used traditional remedies to manage snakebites. The majority (56%) were men and aged >18 y (72%); 59% had low education levels and income. They sourced water from rivers or lakes (93%) and used charcoal as an energy source (74%). These survivors (>67%) resided in households practicing free-range and stall-feeding animal husbandry systems and in houses with thatch roofing or an earthen floor structure. Also, >62% reported muscle tremors, fever and chills, while 80% visited health facilities for further treatment.

CONCLUSION

Community sensitization covering the risks of non-effective remedies and escalation of training to traditional healers could improve the speed of referrals in hard-to-reach snakebite hotspots. Medical anthropology studies could explore the enablers of continued use of traditional remedies in snakebite management in rural communities.

Promoting co-existence between humans and venomous snakes through increasing the herpetological knowledge base

Snakebite incidence at least partly depends on the biology of the snakes involved. However, studies of snake biology have been largely neglected in favour of anthropic factors, with the exception of taxonomy, which has been recognised for some decades to affect the design of antivenoms. Despite this, within-species venom variation and the unpredictability of the correlation with antivenom cross-reactivity has continued to be problematic. Meanwhile, other aspects of snake biology, including behaviour, spatial ecology and activity patterns, distribution, and population demography, which can contribute to snakebite mitigation and prevention, remain underfunded and understudied. Here, we review the literature relevant to these aspects of snakebite and illustrate how demographic, spatial, and behavioural studies can improve our understanding of why snakebites occur and provide evidence for prevention strategies. We identify the large gaps that remain to be filled and urge that, in the future, data and relevant metadata be shared openly via public data repositories so that studies can be properly replicated and data used in future meta-analyses.

Plants Used in Antivenom Therapy in Rural Kenya: Ethnobotany and Future Perspectives

Snake envenomation is one of the neglected tropical diseases which has left an intolerable death toll and severe socioeconomic losses in Kenya. In a continued effort to identify some antiophidic East African botanical species, this study generated ethnobotanical information on antivenom plants reported in Kenya, with a view to identify potential species which could be subjected to in vitro and clinical studies for possible development into antivenoms. Data retrieved through searches done in multidisciplinary databases (Scopus, Web of Science, PubMed, Science Direct, Google Scholar, and Scientific Electronic Library Online) indicated that 54 plant species belonging to 45 genera, distributed among 27 families, are used for the management of snakebites in Kenya. Most species belonged to the family Asteraceae (11%), Malvaceae (11%), Fabaceae (9%), Annonaceae (6%), Combretaceae (6%), and Lamiaceae (6%). The main growth habit of the species is as herbs (35%), shrubs (33%), and trees (28%). Ethnomedicinal preparations used in treating snake poisons are usually from leaves (48%), roots (26%), and stem bark (8%) through decoctions, infusions, powders, and juices which are applied topically or administered orally. The most frequently encountered species were Combretum collinum, Euclea divinorum, Fuerstia africana, Grewia fallax, Microglossa pyrifolia, Solanecio mannii, and Solanum incanum. Indigenous knowledge on medicinal antivenom therapy in Kenya is humongous, and therefore studies to isolate and evaluate the antivenom compounds in the claimed plants are required to enable their confident use in antivenom therapy alongside commercial antivenin sera.