The epidemiology of rabies in Zimbabwe. 2. Rabies in jackals (Canis adustus and Canis mesomelas).

The epidemiology of rabies in Canis adustus (the side-striped jackal) and Canis mesomelas (the black-backed jackal) in Zimbabwe is described using data collected from 1950-1996. Cases in the two species made up 25.2% of all confirmed cases, second only to domestic dogs. Since the species of jackal cases was not recorded on rabies submission forms, the country was divided into areas according to species dominance and jackal cases were assigned to either C. adustus or C. mesomelas dominant zones or a sympatric zone where the relative status of the species is not known. Jackal rabies in both species is maintained in the commercial farming sector. Jackal rabies in the C. adustus zone occurs as dense epidemics, which begin at a single focus and spread centrifugally. The foci were initiated by rabid dogs, but once initiated the epidemic is maintained by C. adustus independently of other species. The extent of outbreaks in the C. adustus zone was limited by geographical (landuse type and jackal species interface) boundaries. Jackal rabies in C. adustus zones showed two seasonal peaks with the main peak occurring during late summer and the second peak during winter. In the C. mesomelas zone jackal rabies was more sparse but it occurred during most years. C. mesomelas is also able to maintain rabies independently of other species, although the epidemiology of the disease in this species is unclear. Transmission of rabies cycles between the two jackal species zones does not appear to occur as epidemics terminate when crossing the C. adustus and C. mesomelas interface boundaries.     

Report of isolations of unusual lyssaviruses (rabies and Mokola virus) identified retrospectively from Zimbabwe

Rabies isolates that had been stored between 1983 and 1997 were examined with a panel of anti-lyssavirus nucleocapsid monoclonal antibodies. Out of 56 isolates from cats and various wild carnivore species, 1 isolate of Mokola virus and 5 other non-typical rabies viruses were identified. The Mokola virus isolate was diagnosed as rabies in 1993 from a cat. Genetic analysis of this isolate suggests that it falls in a distinct subgroup of the Mokola virus genotype. The 5 non-typical rabies viruses were isolated from honey badgers (Mellivora capensis), African civets (Civettictis civetta) and an unidentified mongoose (Herpestidae). These isolates are representatives of rarely-reported wildlife-associated strains of rabies, probably maintained by the slender mongoose (Galerella sanguinea). These findings indicate that both Mokola virus and the mongoose-associated variant may be more common in Zimbabwe than is apparent from routine surveillance.     

A retrospective study of wildlife rabies in Zimbabwe,between 1992 and 2003

To assess the epidemiological features of wildlife rabies in Zimbabwe, a retrospective study covering a period of 12 years (1992–2003) was conducted using rabies records of the Central Veterinary Laboratories (CVL), Department of Veterinary Technical Services at Harare. Records of monthly and annual wildlife rabies were perused with regard to total samples submitted to the CVL and corresponding positive cases. Positive cases were analyzed in relation to the animal species involved, seasonal trends, and land-use categories. A total of 2107 samples were submitted and 1 540 (73.1%) were positive. Jackals (Canis mesomelas and C. adustus), with a peak occurrence of rabies between January and March were the major maintenance host, representing approximately 91% of the total rabies cases confirmed. The Canidae family recorded the highest number of cases followed by the Viverridae, Mustelidae, Felidae, Herpestidae and Hyaenidae families in that order. During the present study rabies cases were confirmed in 7 additional wild animals. The majority of the positive cases (83.7%) were recorded in commercial farming areas in the northeast parts of the country.     

Presence of antibodies to canine distemper virus, canine parvovirus and canine adenovirus type 1 in free-ranging jackals (Canis adustus and Canis mesomelas) in Zimbabwe

A survey of free-ranging jackals (Canis adustus and Canis mesomelas) in Zimbabwe was conducted to determine the prevalence of serum antibodies to canine distemper virus (CDV), canine parvovirus (CPV) and canine adenovirus type 1 (CAV-1). Sera from 16 Canis adustus and 22 Canis mesomelas were collected from 1990 to 1993 from various regions of Zimbabwe and assayed by means of immunofluorescent techniques. Seroprevalence in C. adustus and C. mesomelas respectively were 50% and 63.6% for CDV, 12.5% and 18.2% for CPV and 37.5 and 9.1 for CAV-1. These results demonstrate that jackals are infected with these viruses and may act as reservoirs of them, although their susceptibility to the viruses is not known.     

Age determination in jackals (Canis adustus Sundevall, 1846, andCanis mesomelas Schreber, 1778; Carnivora: Canidae) with reference to the age structure and breeding patterns of jackal populations in Zimbabwe

Methods for determining the age of individual jackals using canine teeth were assessed as part of a study of the population structure of jackal species (side striped jackal, Canis adustus, and black backed jackal, Canis mesomelas), the main wildlife species maintaining rabies in Zimbabwe. Specimens of both species of jackal were obtained from rabies submissions and culling operations, although the major part of the study involved C. adustus. A method of ageing based on relative pulp cavity width of canine teeth differentiated young adults (one year old) from mature adults, but was of no value in determining the age after one year. A method based on cementum incremental growth layers was of no value as the layers were irregular and did not correspond with pulp cavity width. Canis adustus will breed in their first year but no evidence was found to show that C. mesomelas will normally breed at this age. Up to 60 % of C. adustus were young of year jackals, indicating high population turn over and the potential for rapid population recovery following population crashes.     

Vaccinia recombinant virus expressing the rabies virus glycoprotein: safety and efficacy trials in Canadian wildlife.

Twenty-six meadow voles (Microtus pennsylvanicus), ten woodchucks (Marmota monax), thirteen grey squirrels (Sciurus carolinensis), thirteen ring-billed gulls (Larus delawarensis), six red-tailed hawks (Buteo jamaicensis) and eight great horned owls (Bubo virginianus) received vaccinia virus recombinant expressing the rabies virus glycoprotein (V-RG) by direct instillation into the oral cavity. Each of ten coyotes (Canis latrans) received the virus in two vaccine-laden baits. Several voles and most of the gulls died from diseases unrelated to vaccination during the observation period, but all other animals remained healthy and survived. These deaths from causes other than vaccination and the absence of any lesions suggestive of vaccinia infection indicate that it is unlikely that any animal suffered or died as a result of V-RG administration. In addition several animals showed an unexpected high level of rabies neutralizing antibodies.     

Safety evaluation of the SAG2 rabies virus mutant in Tunisian dogs and several non-target species.

The safety of the SAG2 rabies virus, a highly attenuated mutant of the SAD strain intended to vaccinate dogs by the oral route, was evaluated in local Tunisian dogs and in five other local species likely to consume vaccine baits. These species were the domestic cat (Felis catus), the jackal (Canis aureus), the jerboa (Jaculus orientalis), the merion (Meriones sp.) and the gerbil (Gerbillus campestris). The vaccine was administered orally to 21 dogs, 11 cats and eight jackals and orally or intramuscularly to 62 wild rodents of the above-mentioned species. Seven dogs, one cat, five jackals all juvenile and with poor health status) and two rodents died for intercurrent causes. The others were observed for 60-180 days. No animal showed any rabies symptom. Seroneutralizing antibodies were observed in all experimental groups, only after vaccination, with the highest rate being observed in jackals and rodents. The rabies virus was detected in the oral cavity of three cats 6 h after oral instillation, but was not isolated later either in saliva or in salivary glands. Tissue samples (brain and salivary glands) from dead or euthanized animals were examined for the rabies virus antigen by a fluorescent antibody test. No rabies antigen was detected. These trials confirm the safety of the SAG2 strain on the Tunisian species already demonstrated by other authors on many other target and non target species.     

Cell-mediated immune response to rabies virus in dogs following vaccination and challenge

Peripheral blood lymphocytes (PBL) from non-vaccinated dogs and from dogs either vaccinated intramuscularly (IM) or subcutaneously (SC) with an inactivated rabies virus vaccine (Rabguard-TC, Norden Laboratories, Lincoln, NE) or intramuscularly with an attenuated rabies virus vaccine (Endurall-R, Norden Laboratories, Lincoln, NE) were exposed in vitro to rabies virus. Blastogenesis of PBL was measured by incorporation of 3H-thymidine into the DNA of proliferating cells in the presence of a suboptimal concentration of phytohemagglutinin (PHA). Following the first vaccination, there was no difference in the blastogenic response of lymphocytes from dogs vaccinated IM with either the inactivated or attenuated rabies virus vaccines. The inactivated rabies vaccine stimulated as great or greater blastogenic response when it was given SC. The PBL from non-vaccinated control dogs were not stimulated by rabies virus. Dogs vaccinated with the inactivated vaccine developed a lymphocyte blastogenic response to rabies virus following challenge with virulent street rabies virus. Nonvaccinated control dogs did not develop a lymphocyte blastogenic response to rabies virus following challenge with virulent street rabies virus.     

Spill-over of European bat lyssavirus type 1 into a stone marten (Martes foina) in Germany

European bat lyssavirus type 1 (EBLV-1, genotype 5) is known to endemically circulate in insectivorous bat populations in Germany. In August 2001, a rabies suspect stone marten (Martes foina) was found in the city of Burg (Saxony-Anhalt, Germany) and was sent to the regional veterinary laboratory for routine rabies diagnosis. Whereas brain samples repeatedly tested negative in the fluorescent antibody test for classical rabies virus (genotype 1), the mouse inoculation test and the rabies tissue culture inoculation test yielded positive results. Rabies viral RNA was also detected in the stone marten brain sample both by nested and heminested RT-PCR specific for the nucleoprotein gene and for the nucleoprotein phosphoprotein junction of rabies virus. The amplification products were sequenced to genotype the isolate. Sequence data obtained from the first-round RT-PCR products were analysed and the suspect stone marten isolate was confirmed as a rabies related virus (EBLV-1a). Phylogenetic comparison with sequences from recent genotype five isolates from Germany and Denmark showed that it was closely related to a previous isolate of EBLV-1 from a serotine bat in Saxony-Anhalt obtained in the same year in an area adjacent to the place where the EBLV-1 infected stone marten was found. Both EBLV-1 isolates share a 99.5% identity. This is the first report of an EBLV-1a spill-over from an insectivorous bat into wildlife in Europe.     

Spill‐over of European Bat Lyssavirus Type 1 into a Stone Marten (Martes foina) in Germany

European bat lyssavirus type 1 (EBLV‐1, genotype 5) is known to endemically circulate in insectivorous bat populations in Germany. In August 2001, a rabies suspect stone marten (Martes foina) was found in the city of Burg (Saxony‐Anhalt, Germany) and was sent to the regional veterinary laboratory for routine rabies diagnosis. Whereas brain samples repeatedly tested negative in the fluorescent antibody test for classical rabies virus (genotype 1), the mouse inoculation test and the rabies tissue culture inoculation test yielded positive results. Rabies viral RNA was also detected in the stone marten brain sample both by nested and heminested RT‐PCR specific for the nucleoprotein gene and for the nucleoprotein phosphoprotein junction of rabies virus. The amplification products were sequenced to genotype the isolate. Sequence data obtained from the first‐round RT‐PCR products were analysed and the suspect stone marten isolate was confirmed as a rabies related virus (EBLV‐1a). Phylogenetic comparison with sequences from recent genotype five isolates from Germany and Denmark showed that it was closely related to a previous isolate of EBLV‐1 from a serotine bat in Saxony‐Anhalt obtained in the same year in an area adjacent to the place where the EBLV‐1 infected stone marten was found. Both EBLV‐1 isolates share a 99.5% identity. This is the first report of an EBLV‐1a spill‐over from an insectivorous bat into wildlife in Europe.     

Use of vaccinia rabies recombinant for oral vaccination of wildlife

A vaccinia rabies recombinant virus was constructed and shown to induce the synthesis of rabies virus glycoprotein in infected cells and to induce rabies virus neutralizing antibodies and protection in susceptible animals. Active when orally administered, this recombinant is a good candidate for the development of vaccines for wild animal rabies vectors. This recombinant was found stable, safe for target and non-target animal species, and protective for most of the rabies vectors. After extensive experimental studies conducted under controlled conditions, it as used in limited field trials and in an extensive open field trial. The preliminary results confirmed its basic properties and potential for rabies eradication.     

Rabies status in Zambia for the period 1985-2004

Rabies has been present in Zambia since the early years of the 20th century. It is a significant public health problem in Zambia. Domestic dogs accounted for 69.7% (1348/1935) of the samples received for rabies diagnosis for the period 1985-2004. Of the 1069 positive cases confirmed by the fluorescent antibody test, 747 (69.9%) were from domestic dogs, 139 (13.0%) from cattle and 98 (9.2%) from humans. Wildlife samples accounted for 4.5% (87/1935) of the samples tested with the jackal (Canis adustus) being the predominant species. Cases of rabies were highest in Lusaka Province followed by the Copperbelt, Southern and Central Provinces. The monthly distribution of canine rabies showed an average of 2.93 (95% CI 2.59-3.29) dog positive cases per month. The study confirms that rabies is endemic in Zambia and that the domestic dog is the principal maintenance host. The epidemiology and control measures currently used in Zambia are herein discussed highlighting their limitations and successes. Based on the findings obtained from this study we advocate for strengthening the delivery of public health services and that steps must taken to reduce the incidence of rabies in Zambia.     

Polymerase chain reaction and other laboratory techniques in the diagnosis of long incubation rabies in Australia

SUMMARY Blood and post-mortem tissues from a 10-years-old girl were submitted to the Australian Animal Health Laboratory. Clinical signs and histopathological lesions had suggested a diagnosis of rabies, but, an unusually long incubation period of at least 5 years did not encourage such a diagnosis. Serological examinations by the rapid fluorescent focus inhibition test revealed a dramatic increase in rabies virus-neutralising antibody during the 10-day period of hospitalisation. The results of a fluorescent antibody test on brain smears, and an immunoperoxidase test on formalin-fixed sections of brain were also consistent with a diagnosis of rabies. Attempts to isolate virus were unsuccessful. Polymerase chain reactions (PCRs) were conducted on a 10% suspension of a post-mortem sample from the patient's brain, using primers based on the published sequence of the Pasteur virus strain of rabies virus. 413 and 513 bp fragments from the nucleoprotein gene and a 403 bp fragment from the glycoprotein gene were amplified. Subsequent sequencing of these fragments, and comparison with equivalent regions of known rabies viruses, confirmed that the fragments originated from a virus belonging to the rabies virus serotype. This case demonstrated the advantage of using a range of laboratory techniques to obtain a definitive diagnosis. In particular, a PCR-based test may allow a diagnosis, even in the face of conditions that preclude virus isolation such as apparently occurred in this case. Finally, this case demonstrated that an unusually long incubation period should not discourage a tentative clinical diagnosis of rabies.     

狂犬病病毒荧光定量RT-PCR快速检测试剂盒的评价及应用

基于目前在我国人群和动物中流行的狂犬病病毒（RV）均属于基因Ⅰ型,在本室所建立的基因Ⅰ型RV荧光定量RT-PCR方法的基础上,组装了可以便捷使用的RV快速检测试剂盒。对4 577份临床样品的检测结果表明,该试剂盒的检测灵敏度达4.68个TCID50,与《狂犬病防治技术规范》规定的套式RT-PCR灵敏度相当,而且稳定性良好,可以冷冻保存8个月以上。所研制的荧光定量RT-PCR快速检测试剂盒具有操作简便、快速、特异性强、灵敏度高、重复性好、稳定性强等优点,既适合单个临床样品的确诊,又适合RV流行病学监测的大规模筛查。     

Exposure of free-ranging maned wolves (Chrysocyon brachyurus) to infectious and parasitic disease agents in the No?l Kempff Mercado National Park, Bolivia.

Maned wolves (Chrysocyon brachyurus) are neotropic mammals, listed as a CITES Appendix II species, with a distribution south of the Amazon forest from Bolivia, through northern Argentina and Paraguay and into eastern Brazil and northern Uruguay. Primary threats to the survival of free-ranging maned wolves include habitat loss, road kills, and shooting by farmers. An additional threat to the conservation of maned wolves is the risk of morbidity and mortality due to infectious and parasitic diseases. Captive maned wolves are susceptible to, and die from, common infectious diseases of domestic dogs (Canis familiaris) including canine distemper virus (CDV), canine parvovirus (CPV), rabies virus, and canine adenovirus (CAV). Results from this study show that free-ranging maned wolves in a remote area of Bolivia have been exposed to multiple infectious and parasitic agents of domestic carnivores, including CAV, CDV, CPV, canine coronavirus, rabies virus, Leptospira interrogans spp., Toxoplasma gondii, and Dirofilaria immitis, and may be at increased risk for disease due to these agents.     

Molecular epidemiology of rabies in Botswana: a comparison between antibody typing and nucleotide sequence phylogeny

A panel of rabies virus isolates (RABV) endemic within Botswana between 1988 and 1992 have been typed by anti-nucleocapsid monoclonal antibodies (MAb) into two dominant groups. The first associated with the domestic dog (Canis familiaris) and the second associated with a range of wildlife species. Using nucleoprotein coding sequence data, we have applied molecular phylogenetic techniques to the same panel of 35 well-characterised rabies virus isolates from throughout Botswana in an attempt to compare both techniques and to further investigate the virus/host species relationships within this African country. The results confirm that there are indeed two major groups and that these are related primarily to biotype. The wildlife-associated biotype appeared more phylogenetically diverse and was more commonly isolated in the southeast of the country, with the canine-associated group dominating the north of the country. In addition, molecular phylogeny identified further groupings within both biotypes and a small number of isolates, which were not classified by MAb typing, could be assigned to a group. During the study period (4 years) there appeared to be little sequence variation within groups suggesting that distinct lineages persisted throughout the study and that there appears to be little evolutionary pressure on the nucleoprotein coding region of the viral genome.     

Survey of the dog population of Zimbabwe and its level of rabies vaccination

A random sample survey using personal interviews was conducted in Zimbabwe in 1986 to determine the size and structure of the national dog population and its level of rabies vaccination. There was an average of 0.91 dogs per household in Zimbabwe giving an extrapolated total population of 1,308,577 dogs. There was a dog to people ratio of 1:6.5 and an average of 3.4 dogs per square kilometre. The ratio of adult male to female dogs was 0.56:0.44, with 20 per cent of the dog population being less than three months old. In the period 1950 to 1986 there was a 4.7 per cent per annum growth rate of the dog population. In one of the provinces, Manicaland, dogs were found to have an average age of 2.3 years and a life expectancy at birth of 4.6 years. An estimated 40 per cent of the dog population three months old and above had been vaccinated against rabies in 1985/1986. With the rabies incidence in Zimbabwe still unacceptably high this level of vaccination is clearly inadequate and measures designed to increase it are discussed.     

Temporal patterns of domestic and wildlife rabies in central Namibia stock-ranching area, 1986-1996

Eleven years (1986-1996) of wildlife- and domestic-rabies data from the agriculture stock-ranching area of central Namibia were studied using time-series analysis. Nine hundred and sixty three rabies cases were observed in domestic ruminants (5.4 cases/mo), black-backed jackals (Canis mesomelas, 1.3 cases/mo), domestic dogs (0.5 case/mo), and bat-eared foxes (Otocyon megalotis, 0.1 case/mo). The incidence of rabies for all species did not change significantly over the whole study period. However, seasonal variations with an increase in the number of cases between June and November of each year, as well as 34 yr cyclical fluctuations were identified in domestic ruminants and black-backed jackals. The black-backed jackal time-series variable was a significant predictor of the domestic-ruminant and dog time-series variables. The rainfall seasonality combined with the seasonal reproductive pattern of the black-backed jackal appeared to be plausible explanations for the seasonal variations of rabies. However, there was no overall significant correlation between the cyclical weather fluctuations and the 3-4 yr cyclical rabies variations.