Alexandre Dobly

Association between habitat and prevalence of hantavirus infections in bank voles (Myodes glareolus) and wood mice (apodemus sylvaticus)

In order to determine the habitat preferred by Myodes (before Clethrionomys) glareolus and the corresponding Puumala hantavirus seroprevalence in those habitats, we captured rodents simultaneously in three significantly different habitats. We compared trapping success and presence of virus per habitat during an ongoing epidemic in order to test the hypothesis of a density-dependent seroprevalence. Our study showed that bank vole population density, as well as Puumala virus seroprevalence, were habitat dependent. Apodemus sylvaticus was found more vulnerable for deteriorating habitat conditions than M. glareolus and could play a role as vehicle for Puumala virus and as mediator for inter- and conspecific virus transmission.

Trends in genotype frequency resulting from breeding for resistance to classical scrapie in Belgium (2006~2011)

In sheep, susceptibility to scrapie is mainly determined by codons 136, 154, and 171 of the PRNP gene. Five haplotypes are usually present (ARR, ARQ, ARH, AHQ, and VRQ). The ARR haplotype confers the greatest resistance to classical scrapie while VRQ renders animals most susceptible. In 2004, the European Union implemented a breeding program that promotes selection of the ARR haplotype while reducing the incidence of VRQ. From 2006 to 2011 in Belgium, frequency for the ARR/ARR genotypes increased from 38.3% to 63.8% (n = 6,437), the ARQ haplotype diminished from 21.1% to 12.9%, and the VRQ haplotype decreased from 2.0% to 1.7%. The status of codon 141, a determinant for atypical scrapie, was also evaluated. Out of 27 different breeds (n = 5,163), nine were abundant. The ARR/ARR frequency increased in eight of these nine major breeds. The selection program has had a major impact on the ARR haplotype frequency in Belgium. However, the occurrence of atypical scrapie represents a critical point for this program that warrants the continuous monitoring of scrapie. Additionally, genotype frequencies among the breeds varied greatly. Texel, a breed that is common in Belgium, can still be selected for due to its average ARR frequency.

Tick-Borne Encephalitis Virus Seropositive Dog Detected in Belgium: Screening of the Canine Population as Sentinels for Public Health

Tick-borne encephalitis virus (TBEV) is an important emerging tick-borne viral infection of humans and dogs in Europe. Currently, TBEV surveillance is virtually nonexistent in Belgium, which is considered nonendemic. A commercial enzyme-linked immunosorbent assay (ELISA) was adapted for the detection of TBEV-specific IgG-antibodies in canine sera. Serum samples of Belgian dogs were obtained from three diagnostic laboratories from Northern (n=688) and Southern Belgium (n=192). ELISA-positive and borderline samples were subjected to a TBEV rapid fluorescent focus inhibition confirmation test. One dog was confirmed TBEV seropositive. Several ELISA-positive and borderline sera underwent seroneutralization and hemagglutinin inhibition tests to rule out West Nile and Louping Ill viruses, but tested negative. The clinical history of the seropositive dog could not explain beyond doubt where and when TBEV infection was acquired. Further surveillance is necessary to determine whether this dog remains a single travel-related case or whether it represents an early warning of a possible future emergence of TBEV.

Sero-epidemiological study of the presence of hantaviruses in domestic dogs and cats from Belgium

Hantaviruses are worldwide rodent-borne pathogens infecting humans and other animals mainly through inhalation of aerosols contaminated with rodent excreta. Few data are available on hantavirus serology and geographical distribution in dogs and cats. We therefore screened sera from pet dogs (N=410) and cats (N=124) in two regions of Belgium, using IgG ELISA and IFA. We analysed the effect of the owners address as well as pet gender and age on hantavirus status. Hantavirus antibodies were found in both species with a significantly higher seroprevalence in cats than in dogs (16.9% vs. 4.9%, P=0.001). More dogs were infected in highly forested southern Belgium (harbouring more rodents) than in northern Belgium (10.5% vs. 3.0%, P=0.002). In the south, hantavirus sero-positive cats were found in more densely forested localities than sero-negatives ones were (P=0.033). These results are consistent with the ecological variations of hantavirus risks in humans.

Spatiotemporal dynamics of Puumala hantavirus in suburban reservoir rodent populations.

ABSTRACT: The transmission of pathogens to susceptible hosts is dependent on the vector population dynamics. In Europe, bank voles (Myodes glareolus) carry Puumala hantavirus, which causes nephropathia epidemica (NE) in humans. Fluctuations in bank vole populations and epidemics in humans are correlated but the main factors influencing this relationship remain unclear. In Belgium, more NE cases are reported in spring than in autumn. There is also a higher incidence of human infections during years of large vole populations. This study aimed to better understand the link between virus prevalence in the vector, vole demography, habitat quality, and human infections. Three rodent populations in different habitats bordering Brussels city, Belgium, were studied for two years. The seroprevalence in voles was influenced first by season (higher in spring), then by vole density, vole weight (a proxy for age), and capture site but not by year or sex. Moreover, voles with large maximal distance between two captures had a high probability for Puumala seropositivity. Additionally, the local vole density showed similar temporal variations as the number of NE cases in Belgium. These results showed that, while season was the main factor influencing vole seroprevalence, it was not sufficient to explain human risks. Indeed, vole density and weight, as well as the local habitat, were essential to understanding the interactions in these host-pathogen dynamics. This can, in turn, be of importance for assessing the human risks.

Serologic screening for 13 infectious agents in roe deer ( Capreolus capreolus ) in Flanders

Introduction In order to investigate the role of roe deer in the maintenance and transmission of infectious animal and human diseases in Flanders, we conducted a serologic screening in 12 hunting areas. Materials and methods Roe deer sera collected between 2008 and 2013 (n=190) were examined for antibodies against 13 infectious agents, using indirect enzyme-linked immunosorbent assay, virus neutralisation, immunofluorescence, or microagglutination test, depending on the agent. Results and discussion High numbers of seropositives were found for Anaplasma phagocytophilum (45.8%), Toxoplasma gondii (43.2%) and Schmallenberg virus (27.9%), the latter with a distinct temporal distribution pattern following the outbreak in domestic ruminants. Lower antibody prevalence was found for Chlamydia abortus (6.7%), tick-borne encephalitis virus (5.1%), Neospora caninum (4.8%), and Mycobacterium avium subsp paratuberculosis (4.1%). The lowest prevalences were found for Leptospira (1.7%), bovine viral diarrhoea virus 1 (1.3%), and Coxiella burnetii (1.2%). No antibodies were found against Brucella sp., bovine herpesvirus 1, and bluetongue virus. A significant difference in seroprevalence between ages (higher in adults >1 year) was found for N. caninum. Four doubtful reacting sera accounted for a significant difference in seroprevalence between sexes for C. abortus (higher in females). Conclusions Despite the more intensive landscape use in Flanders, the results are consistent with other European studies. Apart from maintaining C. abortus and MAP, roe deer do not seem to play an important role in the epidemiology of the examined zoonotic and domestic animal pathogens. Nevertheless, their meaning as sentinels should not be neglected in the absence of other wild cervid species.

No H- and L-type cases in Belgium in cattle diagnosed with bovine spongiform encephalopathy (1999-2008) aging seven years and older

BackgroundThe bovine spongiform encephalopathy (BSE) epidemic presented homogeneity of the phenotype. This classical BSE (called C-type) was probably due to the contamination of the food chain by a single prion strain. However, due to the active surveillance and better techniques, two rare variants of BSE have been recently reported in different continents without a clear correlation to the BSE epidemic. These emerging types behave as different strains of BSE and were named H-type and L-type according to the high and low molecular mass of the unglycosylated fragment of their proteinase K resistant prion protein (PrPres). In these types, the proportion of the un-, mono- and di-glycosylated fragments of PrP (glycoprofile) is also atypical and represents an effective diagnostic parameter. This study evaluated the presence of such types in bovine of 7 years and older in Belgium.ResultsThe Belgian BSE archive contained 41 bovines of at least 7 years of age. The biochemical features of their PrPres were analyzed by Western blot with five antibodies recognising different regions of PrPres, from N- to C-terminus: 12B2, 9A2, Sha31, SAF84 and 94B4. All antibodies clearly detected PrPres except 12B2 antibody, which is specific for N-terminal region 101-105, a PrP region that is only retained in H-types. The glycoprofiles did correspond to that of C-type (with more than 55% of diglycosylated PrPres using antibody 94B4). Therefore, all cases have the features of C-type BSE.ConclusionsThis study supports that, among the BSE cases of 7 years and older identified in Belgium, none was apparently of the H- or L- type. This is consistent with the very rare occurrence of atypical BSE and the restricted dimension of Belgium. These results shed some light on the worldwide prevalence of atypical BSE.

Breeding suppression between two unrelated and initially unfamiliar females occurs with or without social tolerance in common voles (Microtus arvalis)

Female common voles can breed in small groups or in isolation. Given the option, will isolated females opt for communal breeding with unrelated females and a probable low reproductive bias, or will they remain isolated, forgoing the advantages of group living? This laboratory work examined the response of two unrelated females to a foreign male in order to determine their social and breeding strategies. Before encountering a male, 70% of the females lived communally and 30% were solitary with a dominance hierarchy. In the presence of the male, only 33% of the females were still associated and lived with the male in a communal nest. In the other triads, only the oldest female lived with the male and she dominated the younger female. Although all animals were then experimentally separated to avoid late abortion due to social stress or infanticide, in 89% of the dyads only one female littered. This breeding suppression happened in hierarchic dyads but also in tolerant ones. This laboratory study on the social influence on reproduction showed that breeding suppression can occur in unrelated female common voles even when they are not closely grouped. It suggests that cooperative breeding between unrelated females should remain rare.