[Biogeographical distribution of snakes in Cameroon: the case of venomous snakes]. / Répartition biogéographique des serpents venimeux au Cameroun.

A preliminary analysis of the distribution of snakes captured in Cameroon between 1999 and 2004 is presented in this study. This work helps to provide a better understanding of the distribution of the venomous snakes. The main focus of this study was to identify regions of high diversity of venomous species, a useful step towards developing a national strategy of snakebite care and antivenom distribution. We recorded 4,910 specimens of 150 species from 361 localities throughout Cameroon. Among the ten provinces in Cameroon, the southwest province recorded the highest number of venomous snakes. Diversity was less in the far-north province, but the high abundance of Echis ocellatus seems to be responsible for many snake bites in the region. Of all venomous snakes, the forest cobra Naja melanoleuca was the most abundant in the forest region. The humid savannah region was dominated by Causus maculatus while the Sahelian part by Echis ocellatus. Given the abundance and high snake bite cases of the latter in the region, snakebite care from a national point of view should begin from the far-north towards the forest region of the south-west Cameroon.

[Distribution of antivenoms in Cameroon]. / Distribution des sérums antivenimeux au Cameroun.

Two snake antivenoms are distributed in Cameroon, though their availability in district hospitals varies. These snake antivenoms are FAV-Afrique (Aventis Pasteur) available at Centre Pasteur Cameroun and Polyvalent serum (Serum Institute of India = SII) distributed by a wholesaler (CENAME). The price remains a very important factor. We have noted that some district hospitals do not stock antivenom at all, while others stock very few and sometimes only one vial whereas a good management of snakebite may require up to 14 vials for some envenomations. However, data collected by the CAMHERP project that permit to identify high-risk areas of envenomation might be used as a database for the distribution of snake antivenom in Cameroon.

Anti-inflammatory and analgesic properties of the stem bark extract of Mitragyna ciliata (Rubiaceae) Aubrév. & Pellegr.

Mitragyna ciliata is widely used in traditional medicine for the treatment of inflammation, hypertension, headache, rheumatism, gonorrhoea and broncho-pulmonary diseases. In the present study, the anti-inflammatory and analgesic properties of the stem bark extract of M. ciliata were investigated. The stem bark of this plant was extracted over Soxhlet with hexane followed by another extraction with methanol. The resulting methanol extract was used for the pharmacological test. Anti-inflammatory activity was evaluated on the basis of the inhibitory effect of the extract on 5-lipoxygenase, and carrageenin-induced hind paw oedema in the rat. The methanol extract, at a dose of 19.2 microg/ml, exhibited no inhibition on 5-lipoxygenase. However, this extract administered per os (50 mg/kg) produced about 70% inhibition of carrageenin-induced paw oedema 1 h after administration. This inhibition was maintained to about 50% 2 h after administration. The dose of 50 mg/kg of MeOH extract significantly decreased sensitivity to pain from 78.75 to 107.5 g These findings suggest that extracts of the bark of M. ciliata, possess potent anti-inflammatory and analgesic effects. Chemical analysis of the extract showed the presence of alkaloids and kaempferol derivative which may be responsible for the anti-inflammatory properties.

[Comparative titration of three antivenin serums used against sub-Saharan African snakes]. / Titrage comparatif de trois sérums antivenimeux utilisés contre les serpents d'Afrique sub-saharienne.

The standardisation of serotherapy is necessary in Africa mainly because of the frequency of envenomations and the lack of alternative treatments. Comparative titrations of FAV-Afrique (Aventis Pasteur), Polyvalent serum (Serum Institute of India = SII) and Polyvalent antivenin (South African Vaccine Fabricants Ltd = SAIMR) were carried out on venoms of Echis ocellatus from Cameroun, E. ocellatus from Mali, E. leucogaster and Naja melanoleuca. The 50% protective doses (ED50) of the antivenoms were given according either to i) the in vitro method which consists of inoculating 5 batches of 5 mice with a mixture containing 3 DL50 of venom and increasing volumes of antivenom incubated for 30 mn at 37 degrees C and ii) the in vivo method which consists of successive administration of venom and then antivenom after a 30 to 60 mn interval. The three antivenoms showed a similar efficacy against all the Echis venoms. Interestingly, the SAIMR proved to be effective against the venom of E. leucogaster and E. ocellatus although no venom of Echis was used to immunise horses during the preparation of antivenom. Conversely, this paraspecificity did not exist with the Naja melanoleuca venom against which FAV Afrique showed a higher efficacy. The electrophoresis pattern of FAV-Afrique performed on acetate gel strips showed only one protein fraction (76 g.l-1), whereas both the SII and SAIMR antivenoms showed four fractions whose protein concentrations was respectively 64 g.l-1 and 145 g.l-1.

[Drug or plant substances which antagonize venoms or potentiate antivenins]. / Substances médicamenteuses ou végétales antagonistes du venin ou potentialisant le sérum antivenimeux.

Dendroaspis jamesoni (Elapidae) and Echis oceliatus (Viperidae) are responsible for most of severe evenomation in Cameroon. Toxicity of venoms of these two species has been measured using mice according to the method of Spearman & Kàrber. The effect on experimental envenomation of various drugs (atropine, promethazine, neostigmine, hydrocortisone, pentosane sulfuric polyester, heparin, tranexamic acid and aminocaproic acid) and plant extracts (Schumanniophyton magnificum, Bidens pilosa, Securidaca longepedunculata and Garcinia lucida) has been observed associated or not with the antivenom lpser Afrique (SAV). The venom of D. jamesoni contains neurotoxins agonizing and antagonising acetylcholine. The toxicity of the venom did not depend on the route of injection. Atropine, promethazine, neostigmine and hydrocortisone protected animals against a venom dose up to 2 LD50. Moreover, atropine and promethazine potentiated the SAV. Similar results have been obtained with extracts from S. magnificum and B. pilosa. The venom of E. ocellatus induces haemorrhage and necrosis. The toxicity increased by 3-fold when the venom was injected through intravenous or intraperitoneal route, compared to intramuscular route. Pentosane sulfuric polyester and tranexamic acid protected mice against doses up to 3 LD50. Pentosane sulfuric polyester, hydrocortisone, heparin and aminocaproic acid increased the SAV protective titre by 50%. However, tried plant extracts weakly antagonised the venom and did not potentiate the SAV.