New evidence of a lateral transfer of monogenean parasite between distant fish hosts in Lake Ossa, South Cameroon: the case of Quadriacanthus euzeti n. sp.

Species of the monogenean genus Quadriacanthus mainly infect fish belonging to the Siluriformes, especially the genera Clarias, Heterobranchus or Bagrus, and their host specificity is strict (oioxenous) or narrow (stenoxenous). An examination of the gills of 19 Papyrocranus afer from Lake Ossa, South Cameroon, revealed for the first time the presence of a species of Quadriacanthus from a fish host belonging to the Notopteridae. The morphology and the size of sclerotized parts of haptor and the male and female copulatory complexes suggest that this monogenean is a new species named Quadriacanthus euzeti n. sp. The fish genus Papyrocranus differs taxonomically from the usual fish hosts of Quadriacanthus and hence the presence of a species belonging to this genus on the gills of this host suggests the occurrence of a lateral transfer of Quadriacanthus from species belonging to Clarias or Bagrus which live sympatrically with P. afer in Lake Ossa.

In vitro anthelminthic efficacy of Dichrocephala integrifolia (Asteraceae) extracts on the gastro-intestinal nematode parasite of mice: Heligmosomoides bakeri (Nematoda, Heligmosomatidae).

OBJECTIVE: To evaluate the ovicidal and larvicidal activities of aqueous and ethanolic extracts of leaves of Dichrocephala integrifolia (D. integrifolia) against the eggs (fresh and embryonnated), the first and second larval stages of Heligmosomoides bakeri. In order to verify if this medicinal plant possesses active compounds capable of inhibiting the embryonation and hatching of eggs or to induce the mortality of larvae (L1 and L2). METHODS: dried extracts were diluted in distilled FIV water to obtain five different concentrations: 625, 1,250, 2,500, 3,750 and 5,000 µg/mL. Fresh eggs obtained from artificially infected mice feces were exposed to these different concentrations for 48 h. Time of contact for embryonated eggs was 6 h while L1 and L2 larvae were exposed for 24 h. Distilled water (placebo) and 1.5% DMSO were used as negative controls. RESULTS: Distilled water, and 1.5% DMSO had no effect on embryonation, hatching and larval survival. Aqueous extracts of D. integrifolia showed a weak activity against all stages of the parasite at all concentrations tested. On the contrary, the ethanolic extract of D. integrifolia inhibited the embryonation of 87.5% of fresh eggs, the hatching of 81.1% of embryonated eggs and induced the mortality of 98.1% and 98% of L1 and L2 larvae respectively at 5,000 µg/mL. CONCLUSIONS: The results of the present study indicate that the ethanolic extracts of D. integrifolia contained compounds with ovicidal and larvicidal properties. In spite of these results, in vivo tests, studies on toxicity and mechanism of action of active compounds are also needed to validate the utilisation of this medicinal plant by population of Dschang-Cameroon to treat gastro-intestinal parasites.

A comparative study of the ovicidal and larvicidal activities of aqueous and ethanolic extracts of pawpaw seeds Carica papaya (Caricaceae) on Heligmosomoides bakeri.

OBJECTIVE: To assess the ovicidal and larvicidal activities of aqueous and ethanolic extracts of pawpaw seeds Carica papaya (Caricaceae) on the eggs and first stage larvae (L(1)) of Heligmosomoides bakeri. METHODS: Eggs of this parasite were obtained from experimentally infested mice (Mus musculus) and larvae were from eggs after incubation at 25∘C for about 72 hours. The eggs and larvae were exposed to ten different concentrations (0.125, 0.25, 0.375, 0.5, 0.75, 1.0, 1.25, 1.75, 2.25 and 2.75 mg/mL) of both aqueous and ethanolic extracts respectively for 72 hours. Distilled water and 0.05% ethanol used as placebo and negative control, respectively. RESULTS: Placebo and negative control group all showed average 92% embryonnation, 98% egg hatching and 2% larval mortality, and did not affect development and larval survival. The extracts inhibited embryonic development, egg hatching and larval survival. In general, the ovicidal and larvicidal activities increased with increasing concentration of different extracts. The aqueous extract was found to be more potent on eggs than on larvae. At 2.75 mg/mL, only 8% of eggs embryonnated and 50% hatched to L(1) vs 57% embryonic development and 79% hatching occurred in the ethanolic extract. However, this later extract was more efficient in preventing larval development producing 96% mortality as against 68% with the aqueous extract. CONCLUSIONS: These results shows the ovicidal and larvicidal properties of aqueous and ethanolic pawpaw seeds extracts.

The In Vitro Effects of Aqueous and Ethanolic Extracts of the Leaves of Ageratum conyzoides (Asteraceae) on Three Life Cycle Stages of the Parasitic Nematode Heligmosomoides bakeri (Nematoda: Heligmosomatidae).

A comparative in vitro study was carried out to determine the ovicidal and larvicidal activity of aqueous and ethanolic extracts of Ageratum conyzoides (Asteraceae) leaves on the eggs (unembryonated and embryonated), first and second larval stages of Heligmosomoides bakeri. Four different concentrations (0.625, 1.25, 2.5, and 3.75 mg·mL(-1)) of both aqueous and ethanolic extracts were tested. Distilled water and 5% tween were used as negative controls in the bioassay. In fact, they did not affect development of eggs, hatching, and larval survival. The extract activities were dose dependent. The ethanolic extract was more potent against embryonation (39.6 ± 2.9%) than the aqueous extract (53.3 ± 10.9%) at the highest concentration (3.75 mg·ml(-1)). Both types of extracts killed larvae. Mebendazole proved more lethal (EC(50) of 0.745 and 0.323 mg·mL(-1), resp., for L(1) and L(2) larvae). The aqueous extracts were the least lethal (EC(50) of 4.76 and 2.29 mg·mL(-1), resp., for L(1) and L(2) larvae). The ethanolic extracts showed intermediate activity (EC(50) of 1.323 and 1.511 mg·mL(-1), resp., for L(1) and L(2) larvae). It is concluded that the ovicidal and larvicidal properties of aqueous and ethanolic extracts of Ageratum conyzoides leaves are demonstrated in this work.

In vitro activities of acetonic extracts from leaves of three forage legumes (Calliandra calotyrsus, Gliricidia sepium and Leucaena diversifolia) on Haemonchus contortus.

OBJECTIVE: To assess ovicidal activity of three acetonic extracts from the leaves of three forage legume, Calliandra calotyrsus (C. calotyrsus), Gliricidia sepium (G. sepium) and Leucaena diversifolia (L. diversifolia) in vitro on Haemonchus contortus (H. contortus). METHODS: Eggs were exposed for 24 hours to five different concentrations (0.075, 0.15, 0.3, 0.6 and 1.25 mg/mL) of acetonic extracts at room temperature (24 °C). Distilled water and 0.4% Tween were used in the bioassay as negative controls. RESULTS: The later did not affect embryonation and egg hatching of H. contortus. Conversively, significant effects were obtained with the acetonic extracts of leaves of all three plants and the maximum activity was observed with the highest concentration (1.25 mg/mL). The acetonic extract of G. sepium was found to be more active (2.9% and 0.0% for embryonation and egg hatching, respectively) than the other substances 16.5% and 33.5%, respectively for C. calothyrsus, 33.7% and 33.3%, respectively for L. diversifolia. CONCLUSIONS: These results suggest that the three forage legumes do possess ovicidal properties and further studies on larvae should be carried out.

Gill ectoparasites of Barbus martorelli (Teleostean: Cyprinidae) from a tropical watercourse (Cameroon, Africa): conflict or coexistence?

The structure and stability of parasite communities have been mainly explained by high diversity and strong interactions among parasite species. During 16 months, 558 Barbus martorelli gill infracommunities were studied in a tropical zone to determine whether parasite infrapopulations interact. Three levels were retained: the infracommunity level, the gill filament level, and the filament fraction level. Single species infections in Barbus martorelli were very rare and only concerned the core species: Dactylogyrus bopeleti, D. insolitus, D. simplex and Myxobolus barbi. Mixed infections appeared as a general rule in this fish species. Interspecific interactions at all three levels were statistically non significant. Our results suggest that Barbus martorelli gill parasites are non interactive (isolationist).

Prevalence of gastrointestinal parasites in primate bushmeat and pets in Cameroon.

To document the prevalence of gastrointestinal parasites in Cameroonian monkeys and to assess the risk of transmission to humans, we sampled 125 primates belonging to 15 species, of which 78 had been captured for bushmeat in the wild, and 47 were pets kept in urban areas. Seven nematode species, one trematode, one cestode and three protozoa were detected. Eight different parasite species were found in Cercopithecus nictitans and six in C. neglectus, C. pogonias and Cercocebus agilis. Helminths were found in 77% of monkeys, and protozoa in 36%. Trichuris sp. and Entamoeba coli were the most frequent parasites, being found in 54% and 36% of animals, respectively. Helminths were more frequent in adults than in juveniles, while the prevalence of protozoa was not age-related. No significant gender difference was found. Bushmeat monkeys had a significantly higher prevalence of helminth infection than pets (92% versus 51%), whereas there was no significant difference in the prevalence of protozoa (32% versus 43%). Among helminth species, Strongyloides fulleborni was more prevalent in bushmeat monkeys than in pets (55% versus 15%), as were Ancylostoma spp. (62% versus 9%). As these parasites are transmitted transcutaneously by infectious larva, they have a high potential for transmission to humans, during butchering. One pet monkey kept in an urban household in Yaoundé was infected by Schistosoma mansoni. The potential public health implications of these findings are discussed.

In vitro nematicidal activity of extracts of Canthium mannii (Rubiaceae), on different life-cycle stages of Heligmosomoides polygyrus (Nematoda, Heligmosomatidae).

The increasing prevalence of anthelmintic-resistant strains of helminths, drug residues in animal products and high cost of conventional anthelmintics has created an interest in studying medicinal plants as an alternative source of anthelmintic. The potential nematicidal activities of four extracts from the bark of Canthium mannii (Rubiaceae) stem were investigated in vitro. Extracts were diluted in distilled water (DW) to obtain five different concentrations (1.5, 2.0, 2.5, 3.0 and 3.5 mg/ml) and put in contact with eggs and larvae of Heligmosomoides polygyrus. The different stages of the life cycle were also put in contact with the same concentration of mebendazole (MBZ, positive control). One millilitre of each extract at different concentrations and control were added to 1 ml solution containing 30-40 eggs or 10-15 larvae (L1, L2 and L3) and distributed in different Petri dishes. The eggs and larvae were incubated at 24 degrees C and exposure times were: 48 h for un-embryonated eggs, 6 h for embryonated eggs; 2, 4, 6 and 24 h for L1 and L2 larvae, 24-48 h for infective larvae (L3), and 5 days for the larval development test (from L1 to L3). DW and 1% dimethyl sulphoxide (DMSO) were used as placebo and DMSO control, respectively. Significant effects were obtained with three of the four extracts, and differences were observed depending on the parasite stage. Cold water extract (CWE), hot water extract (HWE) and ethanol extract (ETE) inhibited embryonic development (40, 45 and 10%) and hatching of embryonated eggs (40, 85 and 80%), respectively, at 3.5 mg/ml. Only ETE killed L1 (97.18%) and L2 (92.68%) larvae of H. polygyrus after 24 h at 3.5 mg/ml and drastically reduced the production rate (6% at 3.0 and 3.5 mg/ml) of infective larvae (L3) after 5 days of incubation compared to other extracts (P < 0.05). However, the infective larvae of H. polygyrus were resistant to the effect of each of the tested products (extracts and mebendazole). These in vitro results suggested that extracts of C. mannii, used by traditional healers in Dschang, Western Region of Cameroon (Central Africa) to cure intestinal helminthiasis and abdominal pains of their patients, possess nematicidal properties. The active principles responsible for the activity could be secondary metabolites such as alkaloids and saponins present in the extracts. It is suggested that further experiments incorporating in vivo purification of extracts and toxicological investigations should be carried out.

In vivo evaluation of potential nematicidal properties of ethanol extract of Canthium mannii (Rubiaceae) on Heligmosomoides polygyrus parasite of rodents.

The nematicidal activity of ethanol extract (ETE) of Canthium mannii (Rubiaceae) was assessed in vivo compared to that of Mebendazole on the adult of Heligmosomoides polygyrus parasite of rodents. One hundred and five Swiss white mice of two sexes aged 5-6 weeks old, and weighing between 20 and 25 g were orally infected with a 0.8 ml of a dose of 104-120, 1-week-old H. polygyrus infective larvae (L(3)). After the pre-patent period (9-11 days), infected animals were randomly divided into 7 groups of 15 animals each. The nematicidal efficacy of the ETE was monitored through faecal egg count reduction (FECR) and total worm count reduction (TWCR). Five doses (350, 700, 1400, 2800 and 5600 mgkg(-1) body weight) for ETE and 22 mgkg(-1) for Mebendazole were studied using a bioassay. Mebendazole and 3% dimethylsulfoxide (DMSO) were included in the assays as reference drug and placebo, respectively. Each host received according to its weight for 7 days a daily dose of 0.7ml of the product. The ETE for all the doses tested except the dose rate 350 mgkg(-1)bwt was active in vivo on the adult of H. polygyrus and reduced significantly (p<0.05) the FEC and the TWC of the nematode. The dose rate 5600 mgkg(-1)bwt showed the highest nematicidal activity of 75.0% FECR and 83.6% TWCR 7 days post-treatment. These results supported the possible use of medicinal plants in the control of gastro-intestinal helminthiasis.

[Monogeneans from Clarias (Siluriformes, Clariidae) in Cameroon. II. Description of three new species of Birgiellus n gen (Dactylogyridea, Ancyrocephalidae) in the Nyong Basin]. / Monogènes de Clarias (Siluriformes, Clariidae) au Cameroun: II. Description de trois nouvelles espèces du genre Birgiellus n gen (Dactylogyridea, Ancyrocephalidae) dans le bassin du Nyong.

A study of monogenean gill parasites from three species of the genus Clarias Scopoli, 1777 (Clariidae), namely Clarias camerunensis Lönnberg, 1895, C. jaensis Boulenger, 1909 and C. pachynema Boulenger, 1903, from the Nyong Basin (Cameroon) revealed the presence of three new monogenean species of the new genus Birgiellus, namely Birgiellus mutatus n. sp. from C. pachynema, B. calaris n. sp. from C. jaensis and B. kellensis n. sp. from C. camerunensis. The genus Birgiellus differs from the genus Quadriacanthus by the morphology of the ventral bar composed of a single piece (two distinct in Quadriacanthus) and the size of the uncinuli IV, which are not much different from the others (longest in Quadriacanthus). Birgiellus calaris differs from B. mutatus by its ventral anchors longer and larger, the morphology of the ventral bar with a short incision between the two branches, and a long and trapezoid handle, the size of the sclerotised structures of the male and female copulatory organs, the larger thickness of the hook in the male accessory piece, the latter having also a heel. Birgiellus kellensis is closer to B. calaris but can be distinguished by the small size of its dorsal and ventral anchors, its transverse bars, male copulatory organ, and the accessory piece, which also has not a heel but a secondary blade. According to the clause 8.5.2 of the International Zoological Code of Nomenclature (1999) the genus Birgiellus and the species B. mutatus and B. calaris, respectively, replace Claridectes, C. clarisa and C. alacris previously described by Birgi (1987), but whose specimens were not deposited in a museum. All the three taxa described exhibit a strict (oioxenous) host specificity.

[Monogenean parasites from Clariidae (Teleostei, Siluriformes) in Cameroon: I. Description of two new species of Gyrodactylus from the Nyong basin]. / Monogènes parasites de Clariidae (Teleostei, Siluriformes) au Cameroun : I. Description de deux nouvelles espèces du genre Gyrodactylus dans le bassin du Nyong.

The study of gill and skin parasites of three fishes species belonging to the genus Clarias: C. camerunensis, C. jaensis and C. pachynema, from the Nyong basin (Cameroon), revealed the presence of two new Monogenean species of the genus Gyrodactylus Nordmann: G. camerunensis n. sp. and G. nyongensis n. sp. parasite of Clarias camerunensis, C. jaensis and C. pachynema. Gyrodactylus camerunensis n. sp. is clearly distinguished from G. nyongensis n. sp. by the smaller size of the haptor sclerites. These two new species differ also from their closest African relatives of the genus Gyrodactylus, G. rysavyi, G. clarii and G. alberti, by the morphology and size of the haptorail sclerites. Their host specificity was discussed and appeared stenoxenous (mesostenoxenous).

[Experimental study of the compatibility between Schistosoma haematobium and two species of Bulinus in Cameroon]. / Etude expérimentale de la compatibilité entre Schistosoma haematobium et deux espèces de bulins au Cameroun.

A study on the compatibility between Schistosoma haematobium from three remote localities (Mourtourwa, Gounougou and Kékem) and four populations of Bulinus truncatus (Gounougou, Ngaoundéré, Bertoua and Kékem) and four populations of B. globosus (Mourtourwa, Ouroudoukoudje, Bafia and Yaoundé) was undertaken in order to estimate the risk of extension of urinary schistosomiasis in Cameroon. First generation of offspring from wild Bulinus was exposed to miracidia liberated by schistosome eggs extracted from patient urine. Between the 25th and the 60th day post-infestation the number of snails still alive, the number emitting cercariae and the prepatent period duration were noted. Results showed that all B. truncatus samples were susceptible to the three strains of parasite whereas only B. globosus of Mourtourwa and Ouroudoukoudje were susceptible to S. haematobium from Mourtourwa. The schistosome infection rate was then significantly higher in B. truncatus and the prepatent period significantly lower than in B. globosus. The compatibility characterised by a high infection rate and a low prepatent period was significantly better in homopatric couples than in allopatric combinations. The results suggested that B. truncatus might be potentially more implicated than B. globosus to the extension of the urinary bilharziasis in Cameroon.