The biological background of a recurrently emerging infectious disease: prevalence, diversity and host specificity of Avipoxvirus in wild Neotropical birds

Abstract

Understanding which factors promote disease emergence and transmission remains a major challenge of epidemiology. A problem with research on emerging diseases is that we seldom know to what extent pathogens circulate in natural populations before emergence is already occurring. Moreover, it is critical to determine which pathogen characteristics are key to predict their emergence and invasion potential. We examined the prevalence, host specificity and evolutionary relationships of Avipoxvirus causing skin lesions in birds in two megadiverse and unexplored geographical regions of South America: an elevational gradient in the south Ecuadorian Andes, and a lowland Amazon rainforest in French Guiana. Next, we analyzed the host specificity and distribution of the worldwide Avipoxvirus diversity in order to understand their invasion potential. In French Guiana Avipoxvirus prevalence was 0% (n  889, 94 bird species). In Ecuador, prevalence was 0.3% (n  941, 132 bird species), with cases spanning the range of elevations between 1500 and 2500 m. These were caused by two newly described strains, one of which belonged to an American clade of Avipoxvirus shared by different bird families, and another one closely related to a strain recovered from a different family of birds in Madeira. An analysis of the host specificity and geographic distribution of all Avipoxvirus strains known worldwide finds that these viruses are usually host generalists (particularly those in the fowlpox clade), and that many closely related strains are found on multiple continents. Our study at the community level suggests that distantly related Avipoxvirus strains circulate at very low prevalence in continental tropical South America. Avipoxvirus assemblages are composed of generalist strains with different ancestry and widespread distribution, a combination of characteristics which may make these typically scarce viruses perfect candidates to emerge under favorable ecological conditions.

Identification of two novel CRESS DNA viruses associated with an Avipoxvirus lesion of a blue-and-gray Tanager ( Thraupis episcopus )

“…Avipoxvirus has been previously confirmed (KU356758) (Moens et al, 2017), was analysed by RCA to detect a possible coinfection with papillomavirus and various fragments were obtained after digestion with EcoRI (Fig. 1A).…”

“…Interestingly, the nucleotide identity of the ORF encoding TaCV2-Rep even reaches 81 % identity (48% coverage of total rep gene towards the 5-ends) with the Canarypox virus rep gene. This suggests that it is probably a recombinant sequence, where the 5´and 3´ends have distinct evolutionary origins, especially considering the existence of an avipoxvirus identified in the same lesion (Moens et al, 2017). In fact, the existence of recombination of circoviruses Rep-encoding genes from unrelated viruses has been proposed (Gibbs et al, 2006).…”

“…In this paper, we describe a singular yet informative case in which two new genomes of CRESS DNA viruses were isolated from a pox lesion of a common tropical bird, the blue-and-gray tanager (Thraupis episcopus). This bird from which the two new genomes were identified was found infected with an Avipoxvirus strain which caused a cutaneous lesion on the foot (Moens et al, 2017). Moreover we analyze the structure of the genomes and the characterization of the potential ORFs.…”

A Review on the Prevalence of Poxvirus Disease in Free-Living and Captive Wild Birds

“…Nevertheless, some studies in continental areas reveal a wide range in the prevalence of infection, ranging from 0.9 to 12% [15,33,51,55,56]. In contrast, megadiverse tropical regions in Ecuador, French Guiana or Bermuda [54,57,58] show very low prevalences. Traditionally, pox-like lesions and avipox infection prevalences are considered to be higher in islands than in continents.…”

Detection and molecular characterization of Avipoxvirus in Culex spp. (Culicidae) captured in domestic areas in Rio de Janeiro, Brazil

“…Furthermore, APVs can also have relevant impacts on the health of wild bird species. In some cases, APV infections put the conservation of the affected avian species at risk, especially in outbreaks where the virus is introduced in non-adapted ecosystems 7 – 9 .…”