Adenoviruses in Côte d`Ivoire: investigation of diversity and interspecies transmission

Pauly, Maude (2015): Adenoviruses in Côte d`Ivoire: investigation of diversity and interspecies transmission. Dissertation, LMU München: Tierärztliche Fakultät

Abstract

Sub-Saharan Africa is considered to be a hotspot for emerging infectious diseases (EID) and the majority of these EID in humans originated from animal hosts and many are caused by viruses. In this first study on Adenovirus (AdV) in humans and domestic animals in Côte d`Ivoire, not only the prevalence and diversity of AdV shedding was assessed, but also the zoonotic and recombination potential of AdV was elucidated. The study region is situated next to the Taï National Park, the largest tropical forest of Western Africa. During two field missions in 2012, various samples were collected from the local population and from their domestic animals. Moreover the study participants were asked to fill out a questionnaire focusing on exposure to domestic animals and wildlife. Careful observations during the field missions, as well as the statistical analysis of the questionnaires revealed many risk factors for zoonotic disease emergence. Among others the following major drivers for zoonotic EID were identified: frequent contact to body fluids of domestic and wild animals (e.g. of non-human primates), poor hygiene standards (e.g. only limited access to drinking water and clean sanitary facilities), lack of veterinary inspections, insufficient medical care and demographic changes (massive immigration from neighboring countries). Hence we assumed that this region might be the ideal location to investigate whether and how human and animal habitat overlap influences rates and patterns of pathogen transmission between humans, livestock and wildlife. AdV have been detected in mammals, birds, fishes, amphibians and reptiles, worldwide. Even though many AdV infections are asymptomatic in human and animal hosts, AdV-induced symptoms (e.g. gastroenteritis, kerato-konjunctivitis and pneumonitis) have been reported in different species. Bacterial co-infection, young age and immunosuppression enhance the risk to develop severe symptoms. AdV prevalence and diversity in stool samples of humans and rectum/cloacal swabs of various animals (sheep, goat, cow, pig, dog, chickens and monkey) were determined with different PCR systems and subsequent sequencing. By phylogenetic and recombination analyses, the detected AdV strains were characterized, and their phylogenetic relation to recognized AdV types determined. Correlation between AdV infection and disease symptoms, and the effect of age and gender on infection status were analyzed statistically by descriptive statistics and by the application of generalized linear mixed models. The prevalence of human AdV D (HAdV D) in human stool samples in the investigated sites was estimated to be 66 % in CI, 48 % in DR Congo, 28 % in Central African Republic (adults only) and 65 % in Uganda (adults only). Highly diverse HAdV D sequences were identified, among which a number are likely to stand for novel types. Younger individuals were more frequently infected than adults. There was no difference in HAdV D occurrence between genders. Moreover, no correlation was observed between HAdV D infection and clinical symptoms. The overall prevalence of AdV shed was estimated to be 21.7 % for domestic mammals and 42.9 % for chickens. There was no difference in AdV occurrence between age groups. However, female animals were significantly more frequently infected than male animals. Highly diverse and potentially novel AdV apparently circulate among the animal population: strains from 3 different AdV genera Summary 122 (Mastadenovirus, Aviadenovirus and Siadenovirus) were identified and intriguingly HAdV were repeatedly detected in animal rectum swabs. On one hand animals shedding various AdV (including HAdV) can be considered to be reservoir or mixing vessels; on the other hand shedding might only be due to the ingestion of contaminated material and following passive passage. However, it can be assumed that this shedding might play an important role for virus spread and probably for human and animal health. Moreover, potential pathogenicity, modes of transmission, and sources in nature were discussed. To conclude, AdV were detected with a high prevalence and diversity in the human and animal study populations. Further investigations are needed to pinpoint pathological potential of each of the identified viruses. The study findings revealed evidence for anthropozoonotic (human-to-animal) and cross-species transmission of AdV and for recombination. Although no zoonotic transmission (animal-to-human) of AdV was detected, the observed multitude of risk factors for zoonotic transmission certainly favors the cross-species transmission of other pathogens and underlines the importance of research in this potential hotspot for EID. The information gathered may be beneficial in formulating prevention recommendations to reduce pathogen transmission in areas where humans, livestock and wildlife cohabit.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 590 Tiere (Zoologie)
• Fakultäten: Tierärztliche Fakultät
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 31. Januar 2015
• 1. Bericht­erstatter:in: Sutter, Gerd