Systematic Review on Diversity and Distribution of Anopheles Species in Gabon: A Fresh Look at the Potential Malaria Vectors and Perspectives.

Gabon is located in the malaria hyper-endemic zone, where data concerning malaria vector distribution remains fragmentary, making it difficult to implement an effective vector control strategy. Thus, it becomes crucial and urgent to undertake entomological surveys that will allow a better mapping of the Anopheles species present in Gabon. In this review, we examined different articles dealing with Anopheles in Gabon from ProQuest, Web of Science, PubMed, and Google scholar databases. After applying the eligibility criteria to 7543 articles collected from four databases, 42 studies were included that covered a 91-year period of study. The review revealed a wide diversity of Anopheles species in Gabon with a heterogeneous distribution. Indeed, our review revealed the presence of 41 Anopheles species, of which the most abundant were members of the Gambiae and Nili complexes and those of the Funestus and Moucheti groups. However, our review also revealed that the major and minor vectors of malaria in Gabon are present in both sylvatic, rural, and urban environments. The observation of human malaria vectors in sylvatic environments raises the question of the role that the sylvatic environment may play in maintaining malaria transmission in rural and urban areas. Ultimately, it appears that knowledge of biodiversity and spatial distribution of Anopheles mosquitoes is fragmentary in Gabon, suggesting that additional studies are necessary to complete and update these entomological data, which are useful for the implementation of vector control strategies.

Molecular features of hookworm larvae (Necator spp.) raised by coproculture from Ugandan chimpanzees and Gabonese gorillas and humans.

Species composition of Necator hookworms was surveyed in (i) Ugandan chimpanzees living around farms and villages at Bulindi, (ii) Gabonese gorillas under habituation in Moukalaba-Doudou National Park (MDNP), and (iii) Gabonese villagers living adjacent to MDNP. Internal transcribed spacers (ITS) of rDNA and partial cytochrome c oxidase subunit 1 (Cox1) gene of mtDNA were analyzed from larvae obtained by coproculture. Three ITS types (I, II and III) and three Cox1 haplotype groups (A, B and C) were demonstrated. ITS type I and Cox1 haplotype group A, representing Necator americanus, were demonstrated in the hookworm larvae from Gabonese gorillas and humans, but not from Ugandan chimpanzees. Type II and haplotype groups B and C, presumably representing N. gorillae, were found in larvae from Ugandan chimpanzees and Gabonese gorillas and humans. These features were overall similar with those found previously in the Central African Republic. Meanwhile, type III was proven in a larva from a Gabonese gorilla as the first demonstration from a non-human primate. Cox1 haplotypes obtained from Ugandan chimpanzees formed a subgroup within group B, presumably reflecting dispersal and diversification processes of the apes.

Involvement of two genetic lineages of Sarcoptes scabiei mites in a local mange epizootic of wild mammals in Japan.

Similar to wild mammals on the continents, mange caused by the mange mite, Sarcoptes scabiei (Acari: Sarcoptidae) is spreading in wild mammals in most of Japan. We collected crusted or alopetic skin from 120 raccoon dogs (Nyctereutes procyonoides viverrinus), three raccoons (Procyon lotor), six Japanese badgers (Meles anakuma), one Japanese marten (Martes melampus), one stray dog (Canis lupus familiaris), four wild boars (Sus scrofa leucomystax), and one Japanese serow (Capricornis crispus), mainly in an area where mangy wild animals have been increasingly noted in the past 4 yr. The second internal transcribed spacer (ITS2) region of the ribosomal RNA gene and the partial 16S and cytochrome c oxidase subunit I (cox-1) genes of mitochondrial DNA (mtDNA) were characterized in these skin samples. The ITS2 sequencing (404 base pairs [bp]) identified the causative mite for mangy skin lesions of 128 animals as S. scabiei, regardless of host origin. The cat mite (Notoedres cati) was the cause in one raccoon dog and one raccoon. Most mites had almost identical ITS2 nucleotide sequences to those recorded in a variety of mammals worldwide. Partial 16S and cox-1 fragments of mtDNA amplified and sequenced successfully (331 bp and 410 bp, respectively) showed an identical nucleotide sequence except for one site (C vs. T) for the former and four sites (G, C, C, C vs. A, T, T, T, respectively) for the latter fragment. These substitutions were always synchronized, with the two mitochondrial DNA haplotypes (i.e., C/GCCC and T/ATTT) appearing to separately colonize in geographic units. The T/ATTT haplotype fell into a clade where animal-derived mites worldwide dominated, whereas the C/GCCC haplotype formed a geographic branch unique to Japanese isolates. These results suggest that heterologous populations of monospecific S. scabiei are expanding their populations and distributions regardless of host species in an apparently local mange epizootic of wild mammals in Japan.

A distinct genetic population of Gongylonema pulchrum from water buffaloes in Nepal.

Whole-length esophagi of 111 Murrah cross water buffaloes (Bubalus bubalis) were collected in the Kathmandu and Chitwan districts of Nepal from December 2009 to February 2010. Gullet worms showing a typical epithelium-dwelling character were detected in 13 of 53 (24.5%) buffaloes in Kathmandu and in 5 of 58 (8.6%) buffaloes in Chitwan. The worms' morphology and measurements were identical to those of Gongylonema pulchrum Molin, 1857, except for the length of the left spicules relative to the body length. Scanning electron microscopy did not detect any further morphological differences regarding the collected specimen from Nepal compared with G. pulchrum . The ribosomal RNA gene (rDNA), including internal transcribed spacer (ITS) 1 and 2, and a partial region of the cytochrome c oxidase subunit I (COI) of mitochondrial DNA of the worms were characterized and compared with those of G. pulchrum collected from cattle, deer, wild boars, and monkeys in Japan and from cattle in Iran. The 18S, 5.8S, and 28S rDNA nucleotide sequences of the buffalo-collected worms had 99.8% (1,779/1,782), 100% (158/158), and 98.3-98.8% (3,494-3,507/3,551) identities, respectively, with those of G. pulchrum from the other host mammals. The ITS regions exhibited higher variations between the buffalo-collected worms and G. pulchrum from the other host mammals (85-88% identity for ITS1 and 56-80% identity for ITS2). The COI also showed lower identities (89.2-90.2%), although only a single amino acid substitution was noted compared with the majority of G. pulchrum samples collected in Japan. Based on these molecular genetic characters in the rDNA and COI mitochondrial DNA, together with a shorter left spicule length relative to body length, the gullet worms isolated from buffaloes in Nepal might belong to a distinct local or buffalo-preferring population of G. pulchrum, although its geographical distribution on the continent and host specificity remain to be clarified.

Posthodiplostomum sp. Metacercariae in the trunk muscle of northern snakeheads (Channa argus) from the Fushinogawa River, Yamaguchi, Japan.

The northern snakehead Channa argus, native to China, Russia and Korea, is currently found widespread throughout Japan following its original introduction during the 1920s. A parasitological study of 10 snakeheads fished from the Fushinogawa River running through Yamaguchi City, Japan, detected 2-101 (average, 23.7) metacercariae per 100 g of trunk muscle from each fish. The trematode was identified as metacercariae of Posthodiplostomum sp. (Strigeidida: Diplostomidae) morphologically and characterized genetically based on the ribosomal RNA gene (rDNA). Phylogenetic trees were constructed on the basis of either the 18S, ITS or 28S region of rDNA to assess the relationship among members of the family Diplostomidae. The addition of genetic data from more diplostomid taxa, particularly Posthodiplostomum cuticola recorded from a variety of freshwater fish in Eurasia, would facilitate the precise identification of the present species.