Detection of DNA of filariae closely related to Mansonella perstans in faecal samples from wild non-human primates from Cameroon and Gabon

Abstract

Background The Onchocercidae is a family of filarial nematodes with several species of medical or veterinary importance. Microfilariae are found in the blood and/or the dermis and are usually diagnosed in humans by microscopy examination of a blood sample or skin biopsy. The main objectives of this study were to evaluate whether filariae DNA can be detected in faecal samples of wild non-human primates (NHPs), whether the detected parasites were closely related to those infecting humans and whether filarial DNA detection in faeces is associated with co-infections with nematodes (Oesophagostumum sp. and Necator sp.) known to cause blood loss while feeding on the host intestinal mucosa. Methods A total of 315 faecal samples from 6 species of NHPs from Cameroon and Gabon were analysed. PCRs targeted DNA fragments of cox1 and 12S rDNA genes, to detect the presence of filariae, and the internal transcribed spacer 2 (ITS2), to detect the presence of Oesophagostomum sp. and Necator sp. infections. Results Among the 315 samples analysed, 121 produced sequences with > 90% homology with Onchocercidae reference sequences. However, 63% of the 12S rDNA and 78% of the cox1 gene sequences were exploitable for phylogenetic analyses and the amplification of the 12S rDNA gene showed less discriminating power than the amplification of the cox1 fragment. Phylogenetic analyses showed that the cox1 sequences obtained from five chimpanzee DNA faecal samples from Gabon and two from Cameroon cluster together with Mansonella perstans with high bootstrap support. Most of the remaining sequences clustered together within the genus Mansonella, but the species could not be resolved. Among the NHP species investigated, a significant association between filarial DNA detection and Oesophagostomum sp. and Necator sp. infection was observed only in gorillas. Conclusions To our knowledge, this is the first study reporting DNA from Mansonella spp. in faecal samples. Our results raise questions about the diversity and abundance of these parasites in wildlife, their role as sylvatic reservoirs and their potential for zoonotic transmission. Future studies should focus on detecting variants circulating in both human and NHPs, and improve the molecular information to resolve or support taxonomy classification based on morphological descriptions.

Limitations of PCR detection of filarial DNA in human stools from subjects non-infected with soil-transmitted helminths

“…Detection of M. perstans and L. loa Six DNA samples extracted from chimpanzee feces were positive for Mansonella sp., using primers MP-Sen targeting the ITS1, confirming previous results [6]. Although the detection of human DNA is not a guarantee that pathogen DNA has not been degraded, it was successfully amplified in all 52 stool samples.…”

“…To validate this protocol in fecal samples, PCRs targeting a fragment of the ITS1 (using primers Mp-Sen-F and Mp-Sen-R) were also run on six DNA samples extracted from chimpanzees positive for Mansonella sp. (for 12S rDNA or Cox1) [6]. To confirm the results of the stool microscopic examinations, nested or seminested PCRs targeting ITS1 or ITS2 fragments of the STH genomes, respectively, were also run (primers, PCR conditions and references listed in Table 1).…”

“…Recently, Mansonella sp. DNA was detected in fecal samples from non-human primates (NHP) [6]. This study aimed to demonstrate the proof-of-concept of non-invasive diagnosis of human filariasis in stool samples using a conventional PCR method, and to determine whether filarial DNA detection is associated with co-infections with soil-transmitted helminths (STH) causing blood loss while feeding on the host intestinal mucosa.…”

Soil-transmitted helminth infections in free-ranging non-human primates from Cameroon and Gabon

“…1 ). These samples had been characterised and analysed in previous studies to determine the prevalence and genetic diversity of Simian Immunodeficiency Viruses (SIV) [ 35 , 36 ] as well as of filariae [ 37 ]. Experienced trackers and/or the researchers identified most faecal samples to be of chimpanzee and gorilla origin and only a few to be of Cercopithecidae monkey origin.…”

New Molecular Data on Filaria and its Wolbachia from Red Howler Monkeys (Alouatta macconnelli) in French Guiana—A Preliminary Study

“…The cox1 gene enabled the accurate identification of the Mansonella species from wild non-human primates from Cameroon and Gabon [57], and has been proven to be a satisfactory discrimination between filarial species. This gene was described by its low nucleotide distances (from 0 to 0.02) within filarial species [58] and a larger variation between congeneric species (i.e., 0.098 to 0.2) [58,59].…”