The role of non-governmental organisations in controlling rabies: the Global Alliance for Rabies Control, Partners for Rabies Prevention and the Blueprint for Rabies Prevention and Control

Rabies control worldwide has been inadequate and neglected for many decades, and the disease continues to predominantly affect poor communities in Africa and Asia. As a zoonosis for which the main reservoir and vector, the domestic dog (Canis familiaris), is an economically non-viable species, the absence of cross-sectoral cooperation has been a major factor in the lack of effective control efforts. A shift in global focus is required to concentrate on the fact that rabies has the highest case fatality ratio of all infectious human diseases and that it still affects human health more significantly than many other infectious diseases that are perceived to pose more significant risks. Equally necessary is an acknowledgement that rabies control is complex and that the task of creating and executing a strategic plan for the disease can be overwhelming for those governments in the developing world where dog rabies is most problematic. Nonprofit organisations operate independently of governments and intergovernmental organisations and can play a dynamic role in inter-sectoral collaboration and the creation of approaches and strategies for the control of complex diseases such as rabies. In 2008, the Global Alliance for Rabies Control (GARC) established Partners for Rabies Prevention (PRP), a widely representative group of rabies stakeholders and experts, which endeavours to support public-private rabies control activities throughout the world. After a landscape analysis, the PRP proceeded to develop and launch the Blueprint for Rabies Prevention and Control (comprising the Blueprint for Canine Rabies Prevention and Control; the Blueprint for Fox Rabies Prevention and Control and the Rabies Surveillance Blueprint). Subsequently, the Stepwise Approach towards Rabies Elimination (SARE) was embedded into the Canine Rabies Blueprint. The SARE is a planning and self-assessment tool that countries can use to develop activities and monitor progress towards a national programme and strategy for sustainable rabies control and elimination. Each of the elements needed to execute the SARE-derived strategy is cross-linked to the Canine Rabies Blueprint, which provides the specific methods and tools required, supported by references and examples. Together, the Canine Rabies Blueprint and the SARE should be regarded as a novel and dynamic operational toolkit, and a resource that provides comprehensive information for the development and implementation of rabies control strategies, built entirely on the principles of 'One Health'.

Rabies control in KwaZulu-Natal, South Africa

PROBLEM

Urbanization, large dog populations and failed control efforts have contributed to continuing endemicity of dog-mediated rabies in KwaZulu-Natal province, South Africa.

APPROACH

From 2007 to 2014 we used a OneHealth approach to rabies prevention, involving both the human and animal health sectors. We implemented mass vaccination campaigns for dogs to control canine rabies, and strategies to improve rabies awareness and access to postexposure prophylaxis for people exposed to rabies.

LOCAL SETTING

A rabies-endemic region, KwaZulu-Natal is one of the smallest and most populous South African provinces (estimated population 10 900 000). Canine rabies has persisted since its introduction in 1976, causing an average of 9.2 human rabies cases per annum in KwaZulu-Natal from 1976 to 2007, when the project started.

RELEVANT CHANGES

Between 2007 and 2014, the numbers of dog vaccinations rose from 358 611 to 395 000 and human vaccines purchased increased form 100 046 to 156 996. Strategic dog vaccination successfully reduced rabies transmission within dog populations, reducing canine rabies cases from 473 in 2007 to 37 in 2014. Actions taken to reduce the incidence of canine rabies, increase public awareness of rabies and improve delivery of postexposure prophylaxis contributed to reaching zero human rabies cases in KwaZulu-Natal in 2014.

LESSONS LEARNT

Starting small and scaling up enabled us to build strategies that fitted various local settings and to successfully apply a OneHealth approach. Important to the success of the project were employing competent, motivated staff, and providing resources, training and support for field workers.

The Pan-African Rabies Control Network (PARACON): A unified approach to eliminating canine rabies in Africa

Even though Africa has the highest per capita death rate from rabies of any continent, and the disease is almost entirely transmitted by the bites of rabid dogs, there has been no coordinated pan-African approach to controlling canine rabies. In order to attain an inclusive and unified network, the Pan-African Rabies Control Network (PARACON) was established in 2014. By following the 'One Health' concept, which involves close coordination between animal and human health sectors across national, regional and continental levels, PARACON will provide a platform to facilitate and promote coordinated and sustainable control strategies and programmes. Meetings will take place at regular intervals and will be centred on the involvement by key focal persons from the medical and veterinary sectors. The inaugural meeting was held in South Africa in June, 2015 and was focused around interactive discussions and workshops, whilst updating country representatives on the tools available to aid them in developing and implementing sustainable rabies intervention strategies. Experts from various global organizations, institutions and industry participated in the discussions and shared their experience and expertise. The workshops focused on the latest format of the Rabies Blueprint platform (www.rabiesblueprint.com), which in the broadest sense assists with control and elimination campaigns, including educational and advocacy drives, improvement of surveillance and diagnosis and the systematic monitoring of progress. Together with the Stepwise Approach towards Rabies Elimination, the Blueprint is a planning tool to help countries free themselves from canine-transmitted rabies.

Towards Canine Rabies Elimination in KwaZulu-Natal, South Africa: Assessment of Health Economic Data

Rabies remains a significant problem throughout much of the developing world. An estimated 69 000 people die annually from exposure to rabies. Most of these deaths are the result of being bitten by a rabid dog. Mass vaccination campaigns targeting dogs have been implemented around the world in an attempt to control or eliminate canine rabies. We analysed the vaccination and cost data for a campaign in the KwaZulu-Natal province of South Africa; we found that the cost per dog vaccinated to be $6.61 for mass campaigns and $5.41 for local campaigns. We also estimated the cost of human post-exposure prophylaxis (PEP). The cost of PEP is approximately $64.50 on average per patient, and $333 on average for the 9% of patients who receive RIG. We also found that the districts that vaccinated the most dogs per capita experienced the highest rates of human treatment and thus had the highest PEP costs.

High prevalence of antibodies against canine adenovirus (CAV) type 2 in domestic dog populations in South Africa precludes the use of CAV-based recombinant rabies vaccines

Rabies in dogs can be controlled through mass vaccination. Oral vaccination of domestic dogs would be useful in the developing world, where greater vaccination coverage is needed especially in inaccessible areas or places with large numbers of free-roaming dogs. From this perspective, recent research has focused on development of new recombinant vaccines that can be administered orally in a bait to be used as adjunct for parenteral vaccination. One such candidate, a recombinant canine adenovirus type 2 vaccine expressing the rabies virus glycoprotein (CAV2-RG), is considered a promising option for dogs, given host specificity and safety. To assess the potential use of this vaccine in domestic dog populations, we investigated the prevalence of antibodies against canine adenovirus type 2 in South African dogs. Blood was collected from 241 dogs from the Gauteng and KwaZulu-Natal provinces. Sampled dogs had not previously been vaccinated against canine adenovirus type 1 (CAV1) or canine adenovirus type 2 (CAV2). Animals from both provinces had a high percentage of seropositivity (45% and 62%), suggesting that CAV2 circulates extensively among domestic dog populations in South Africa. Given this finding, we evaluated the effect of pre-existing CAV-specific antibodies on the efficacy of the CAV2-RG vaccine delivered via the oral route in dogs. Purpose-bred Beagle dogs, which received prior vaccination against canine parvovirus, canine distemper virus and CAV, were immunized by oral administration of CAV2-RG. After rabies virus (RABV) infection all animals, except one vaccinated dog, developed rabies. This study demonstrated that pre-existing antibodies against CAV, such as naturally occurs in South African dogs, inhibits the development of neutralizing antibodies against RABV when immunized with a CAV-based rabies recombinant vaccine.

A case study of rabies diagnosis from formalin-fixed brain material

Rabies is caused by several Lyssavirus species, a group of negative sense RNA viruses. Although rabies is preventable, it is often neglected particularly in developing countries in the face of many competing public and veterinary health priorities. Epidemiological information based on laboratory-based surveillance data is critical to adequately strategise control and prevention plans. In this regard the fluorescent antibody test for rabies virus antigen in brain tissues is still considered the basic requirement for laboratory confirmation of animal cases. Occasionally brain tissues from suspected rabid animals are still submitted in formalin, although this has been discouraged for a number of years. Immunohistochemical testing or a modified fluorescent antibody technique can be performed on such samples. However, this method is cumbersome and cannot distinguish between different Lyssavirus species. Owing to RNA degradation in formalin-fixed tissues, conventional RT-PCR methodologies have also been proven to be unreliable. This report is concerned with a rabies case in a domestic dog from an area in South Africa where rabies is not common. Typing of the virus involved was therefore important, but the only available sample was submitted as a formalin-fixed specimen. A real-time RT-PCR method was therefore applied and it was possible to confirm rabies and obtain phylogenetic information that indicated a close relationship between this virus and the canid rabies virus variants from another province (KwaZulu-Natal) in South Africa.

Soybean blotchy mosaic virus, a New Cytorhabdovirus Found in South Africa

A previously unidentified plant Rhabdovirus sp. associated with a blotchy mosaic symptom of soybean (Glycine max), prevalent in the lower-lying, warmer soybean production areas of South Africa, was isolated and partially characterized. The virus was shown to be transmitted by mechanical inoculation and at least one species of leafhopper (Peragallia caboverdensis Lindberg (Cicadellidae, Agalliinae)). To determine the morphology and virion size, as well as intercellular accumulation, negative-stained preparations or embedded ultrathin sections of infected plant samples were observed under a transmission electron microscope. The distribution of the virions within the cytoplasm and its bullet-shaped morphology and size (338 to 371 nm by 93 nm) suggested that it is a putative member of the genus Cytorhabdovirus. Degenerate primers designed to a conserved region of the polymerase gene of a number of Rhabdovirus spp. were used in reverse-transcriptase polymerase chain reaction with total RNA from symptomatic plants as template. Amplicons were sequenced and compared with related sequences available on GenBank. The analysis confirmed that the virus was related to Cytorhabdovirus spp., with the highest nucleotide similarity being 60.7% with Northern cereal mosaic virus. The particle morphology, typical virion accumulation in the cytoplasm of infected cells, nucleotide sequence similarity with that of other plant Rhabdovirus spp., and unique symptoms on soybean suggest that the virus is a previously unknown Cytorhabdovirus sp., for which we propose the name Soybean blotchy mosaic virus (SbBMV).

Evaluation of a rapid immunodiagnostic test kit for detection of African lyssaviruses from brain material

A rapid immunodiagnostic test kit was evaluated against a selection of isolates of lyssavirus genotypes occurring in Africa. The test was carried out in parallel comparison with the fluorescent antibody test (FAT) and isolates representing previously established phylogenetic groups from each genotype were included. The specificity of the rapid immunodiagnostic test compared favourably with the FAT and was found to detect all representatives of genotypes 1, 2, 3 and 4 in brain samples of either field cases or suckling mouse brain inoculates.

Evolutionary history of African mongoose rabies

Two biotypes or variants of rabies virus (RABV) occur in southern Africa. These variants are respectively adapted to hosts belonging to the Canidae family (the canid variant) and hosts belonging to the Herpestidae family (the mongoose variant). Due to the distinct host adaptation and differences in epidemiology and pathogenesis, it has been hypothesized that the two variants were introduced into Africa at different times. The objective of this study was to investigate the molecular phylogeny of representative RABV isolates of the mongoose variant towards a better understanding of the origins of this group. The study was based on an analysis of the full nucleoprotein and glycoprotein gene sequences of a panel of 27 viruses. Phylogenetic analysis of this dataset confirmed extended evolutionary adaptation of isolates in specific geographic areas. The evolutionary dynamics of this virus variant was investigated using Bayesian methodology, allowing for rate variation among viral lineages. Molecular clock analysis estimated the age of the African mongoose RABV to be approximately 200 years old, which is in concurrence with literature describing rabies in mongooses since the early 1800 s.

Molecular epidemiology of rabies: focus on domestic dogs (Canis familiaris) and black-backed jackals (Canis mesomelas) from northern South Africa

Phylogenetic relationships of rabies viruses recovered from black-backed jackals (Canis mesomelas) and domestic dogs (Canis familiaris) in northern South Africa were investigated to determine whether the black-backed jackal is an emerging maintenance host species for rabies in this region. A panel of 123 rabies viruses obtained from the two host species between 1980 and 2006 were characterised by nucleotide sequencing of the cytoplasmic domain of the glycoprotein gene and the non-coding G-L intergenic region. Through phylogenetic analysis a viral cluster specific to black-backed jackals and spanning a 5-year period was delineated in western Limpopo. Virus strains associated with domestic dogs prevail in densely populated communal areas in north-eastern Limpopo and in south and eastern Mpumalanga. The data presented in this study indicated the likelihood that black-backed jackals are capable of sustaining rabies cycles independent of domestic dogs. It is proposed that wildlife rabies control strategies, in synergy with domestic animal vaccination should be considered for effective control of rabies in South Africa.

Transmission of Activated-Episomal Banana streak OL (badna)virus (BSOLV) to cv. Williams Banana (Musa sp.) by Three Mealybug Species

Four different mealybug species (Dysmicoccus brevipes, Planococcus citri, P. ficus, and Pseudococcus longispinus) were evaluated for their ability to transmit putative activated-episomal Banana streak OL (badna)virus (BSOLV) to banana cv. Williams (Cavendish subgroup, AAA). Expressible endogenous sequences of banana streak viruses (BSVs) have been reported to be present in the DNA of various Musa hybrids, including FHIA-21 (AAAB). To obtain activated episomal BSOLV for this experimental transmission study, intentional stress by tissue culture propagation was applied to indexed FHIA-21 which, while free of other viruses, can contain activated episomal BSOLV. Immunocapture polymerase chain reaction and triple-antibody sandwich enzyme-linked immunosorbent assay results revealed that 13.4% of the derived progeny of the mother plants were infected with episomal BSOLV. Four of these BSOLV-infected progeny were used as sources of episomal virus for transmission studies. D. brevipes, Planococcus citri, and P. ficus mealybugs were able to transmit the putative activated episomal BSOLV. Control plants for the transmission experiments included FHIA-21 corms with no background history of tissue culture, as well as virus-free Williams plants. Episomal Banana streak GF (badna)virus (BSGFV) was transmitted from asymptomatic corm-derived FHIA-21 plants by P. citri and P. ficus. This is the first report of P. ficus as a vector of BSVs.

Cross-protective and cross-reactive immune responses to recombinant vaccinia viruses expressing full-length lyssavirus glycoprotein genes

Lyssaviruses cause acute, progressive encephalitis in mammals. Current rabies vaccines offer protection against the lyssaviruses, with the notable exceptions of Mokola virus (MOKV), Lagos bat virus (LBV) and West Caucasian bat virus (WCBV). Here we describe the cross-protective and cross-reactive immune responses induced by experimental recombinant vaccinia viruses encoding the glycoprotein genes of rabies virus (RABV), MOKV and WCBV, either singly or in dual combinations. Constructs expressing a single glycoprotein gene protected mice against lethal intracranial challenge with homologous virus. Similarly, recombinants expressing glycoprotein genes from two different lyssaviruses offered mice protection against both homologous viruses. VNAb induced by vaccines that included a MOKV glycoprotein gene cross-neutralized LBV, but not WCBV. We concluded that a single recombinant poxvirus-vectored vaccine including MOKV and RABV glycoprotein genes, should be a major addition to available rabies biologics and should offer broad protection against all of the lyssaviruses, except WCBV.

Phylogeny of Lagos bat virus: challenges for lyssavirus taxonomy

Lagos bat virus (LBV) belongs to genotype 2 of the Lyssavirus genus. The complete nucleoprotein (N), phosphoprotein (P), matrixprotein (M) and glycoprotein (G) genes of 13 LBV isolates were sequenced and phylogenetically compared with other lyssavirus representatives. The results identified three different lineages of LBV. One of these lineages demonstrated sufficient sequence diversity to be considered a new lyssavirus genotype (Dakar bat lyssavirus). The suggested quantitative separation of lyssavirus genotypes using the N, P, M and G genes was also investigated using P-distances matrixes. Results indicated that the current criteria should be revised since overlaps between intergenotypic and intragenotypic variation occur.

Can rabies be eradicated?

Rabies, an acute progressive encephalitis, is an ancient zoonosis. Its distribution encompasses all continents, except Antarctica. Agents consist of at least 11 species orgenotypes of rhabdoviruses, in the Genus Lyssavirus. Susceptible natural hosts include all mammals. Primary reservoirs reside in the Orders Carnivora and Chiroptera. A plethora of variants, maintained by a diversity of abundant hosts, presents a challenge to a strict concept of true eradication. Globally, the domestic dog remains the most significant species for viral transmission, responsible for millions of suspect human exposures and tens of thousands of fatalities. As such, this single major target provides an ideal opportunity for focused intervention programmes in humane disease prevention and control, driven by laboratory-based surveillance and guided via modern epidemiological insights. Historically, substantial technical progress throughout the 20th century led to the development of safe, affordable and efficacious animal and human vaccines, resulting in declining disease burdens in selected developed and developing countries. Regional and local disease resurgence occurs, due in part to a combination of political and economic instability, environmental perturbations, and shifting government priorities. Society must recall that despite the recent recognition of other important emerging infectious diseases, none exceed the case fatality rate of rabies. Given the clear relevance of rabies in public health, agriculture, and conservation biology, substantive international progress must continue towards enhanced public awareness, human rabies prevention, wildlife rabies control, and canine rabies elimination, with renewed collaborative vigour.

Epidemiology and pathogenicity of African bat lyssaviruses

Lyssaviruses belonging to all four known African Lyssavirus genotypes (gts) have been reported and isolated from SouthAfrica over the past few decades. These are: (1) Duvenhage virus (gt4), isolated again in 2006 from a human fatality; (2) Mokola virus (gt3), isolated irregularly, mostly from cats; (3) Lagos bat virus (gt2) continually isolated over the past four years from Epomophorus fruit bats and from incidental terrestrial animals and (4) Rabies virus (gt1) - with two virus biotypes endemic in mongoose and in canid species (mostly domestic dogs, jackals and bat-eared foxes), respectively. Only two of these are associated with bats in Southern Africa, viz. Duvenhage virus and Lagos bat virus (gts 4 and 2). For both these genotypes the authors have embarked on a programme of comparative study of molecular epidemiology. Duvenhage virus nucleoprotein nucleotide sequence analysis indicated a very low nucleotide diversity even though isolates were isolated decades apart. In contrast, individual isolates of Lagos bat virus were found to differ significantly with respectto nucleoprotein gene nucleotide sequence diversity as well as in pathogenicity profiles.

Molecular epidemiology of rabies in bat-eared foxes (Otocyon megalotis) in South Africa

A panel of 124 rabies viruses from wildlife host species (principally the bat-eared fox, Otocyon megalotis) and domestic carnivore species were collected between 1980 and 2005 from a region of South Africa associated with endemic bat-eared fox rabies. We have studied the molecular epidemiology of bat-eared fox rabies by virtue of nucleotide sequence analyses of PCR amplicons specific to the variable G-L intergenic region as well as the conserved nucleoprotein gene of each of the rabies viruses in this South African panel. Although it was demonstrated that all of these viruses were very closely related, they could be segregated into two major phylogenetic groups. The data presented in this paper complement antigenic and surveillance data on rabies in this host species in South Africa. Most importantly our data support a hypothesis that the bat-eared fox independently maintains rabies cycles in specific geographical loci. This is the first molecular epidemiological investigation describing rabies transmission dynamics in this wildlife carnivore host species in South Africa.

Emergence of lyssaviruses in the Old World: the case of Africa

Rabies has a long history of occurrence throughout Africa, spanning hundreds of years. At least four distinct Lyssavirus species persist throughout the continent, among carnivores, bats and other mammals. Rabies virus is the most cosmopolitan member, with primary reservoirs within dogs and mongoose, but other wildlife vectors are important in viral maintenance, such as jackals. Besides a prominent toll on humans and domestic animals, the disease has an underappreciated role in conservation biology, especially for such highly endangered fauna as African wild dogs and Ethiopian wolves. Both Duvenhage and Lagos bat viruses are adapted to bats, but their epidemiology, together with Mokola virus, is poorly understood. Significantly, less than ideal cross-reactivity with modern biologicals used for veterinary and public health interventions is a major cause for concern among these emerging viral agents.

Mongoose rabies in southern Africa: a re-evaluation based on molecular epidemiology

Relative to the developed world, rabies has been poorly studied in the vast African continent. The southern African countries of Zimbabwe and South Africa, however, are known to sustain a great diversity of lyssaviruses, with large biological variations amongst genotype 1 (rabies viruses) at present more apparent here than elsewhere on the continent. One recognized biotype of rabies virus in the subcontinent appears to be specifically adapted to a variety of mongooses, belonging to the Viverrinae subfamily (family Herpestidae) and are commonly referred to as viverrid viruses, although the term mongoose rabies would be more correct, considering the taxonomic status of the host species involved. It was our objective to study the genetic relationships of 77 rabies virus isolates of this mongoose biotype, isolated in South Africa and Zimbabwe, towards elucidation of the molecular epidemiology of this interesting group of African viruses. In our study of a 592 nucleotide sequence encompassing the cytoplasmic domain of the glycoprotein and the G-L intergenic region of the viral genomes, we provide the first comprehensive data on the molecular epidemiology of these viruses and indicate a history of extended evolutionary adaptation in this geographical domain. The molecular epidemiological observations reported here are highly unlikely to be limited to the small geographical areas of South Africa and Zimbabwe and illustrate the need for lyssavirus surveillance in the rest of sub-Saharan Africa and throughout the entire continent.

Segment specific inverted repeat sequences in bluetongue virus mRNA are required for interaction with the virus non structural protein NS2

Computational secondary structure prediction of all 10 Bluetongue virus (BTV-10) RNA transcripts and mutant inverted repeat transcripts were performed. Transcripts with intact 5' and 3' inverted repeat sequences, all indicated base-pairing between the 5' and 3' ends when optimal folding parameters were applied. Secondary structure analysis of the mutant transcripts lacking the inverted repeat sequences indicated alterations in the secondary structures resulting from altered base-pairing. The importance of the inverted repeat sequences in RNA--protein binding was subsequently investigated. Deletion mutant clones lacking the 5' and/or 3' inverted repeat sequences have been constructed. A baculovirus recombinant expressing the BTV NS2 protein and radioactively synthesized RNA transcripts were subjected to nitrocellulose RNA--protein binding assays. The cumulative results suggested that the inverted repeat deletion mutants display weaker binding compared to BTV-10 segment 8 with intact 5' and 3' inverted repeat sequences. Inverted repeats may influence RNA--protein binding by altering the secondary structure of the RNA and consequently the specific NS2 protein-binding sites may no longer be available.

PCR-based detection of the transovarial transmission of Uruguayan Babesia bovis and Babesia bigemina vaccine strains

Bovine babesiosis is responsible for serious economic losses in Uruguay. Haemovaccines play an important role in disease prevention, but concern has been raised about their use. It is feared that the attenuated Babesia bovis and Babesia bigemina vaccine strains may be transmitted by the local tick vector Boophilus microplus, and that reversion to virulence could occur. We therefore investigated the possibility that these strains could be transmitted via the transovarial route in ticks using a Babesia species-specific polymerase chain reaction (PCR) assay. DNA was extracted from the developmental stages of the tick vector that had fed on calves immunized with the haemovaccine. It was possible to detect Babesia DNA not only in adult ticks, but also in their eggs and larvae. In addition, it was shown that calves infested with larvae derived from eggs laid by ticks fed on acutely infected calves, were positive for Babesia using PCR. Caution should therefore be shown with the distribution of the haemovaccine in marginal areas. It is still advisable that suitable tick control measures be used to prevent transovarial transmission and the potential risk of attenuated Babesia reverting to virulence.

A comparison of DNA vaccines for the rabies-related virus, Mokola

Mokola virus, a rabies-related virus, has been reported to date from the African continent only. Like rabies virus, it is highly pathogenic, causes acute encephalitis, and zoonotic events have been documented. Although believed to be rare, there has been an unexplained increase in the number of isolations of the virus in South Africa in recent years. We have cloned and sequenced the glycoprotein (G) and nucleoprotein (N) genes from a South African Mokola virus, and used these in the construction of different DNA vaccines for immunization against Mokola virus. Four vaccines, utilizing different promoters and DNA backbone compositions, were generated and compared for efficacy in protection against Mokola virus. In one of these, both the Mokola virus G and N genes were co-expressed. Two of the single G-expressing DNA vaccines (based on pSG5 and pCI-neo, respectively) protected laboratory mice against lethal challenge, despite major differences in their promoters. However, neither vaccine was fully protective in a single immunization only. Serological assays confirmed titers of virus-neutralizing antibodies after immunization, which increased upon booster vaccine administration. A third construct (based on pBudCE4) was less effective in inducing a protective immune response, despite employing a strong CMV enhancer/promoter also used in the pCI-neo plasmid. Dual expression of Mokola virus G and N genes in pBudCE4 did not enhance its efficacy, under the conditions described. In addition, no significant utility could be demonstrated for a combined prime-boost approach, as no cross-protective immunity was observed against rabies or Mokola viruses from the use of pSG5-mokG or vaccinia-rabies glycoprotein recombinant virus vaccines, respectively, even though both vaccines provided 60-100% protection against homologous virus challenge.

Identification methods for Legionella from environmental samples

Laboratories responsible for Legionella diagnostics around the world use a number of different culturing methods of non-equivalent sensitivities and specificities, to detect Legionella species in environmental samples. Specific countries usually standardize and use one approved method. For example, laboratories in Australia use the Australian Standard (AS) method and those in Europe, the International Standard method (ISO). However, no standard culturing methods have been established in South Africa to date. As a result, there is uncertainty about the true prevalence and most common species of Legionella present in the South African environment. In an attempt to provide guidelines for the development of a standard method specific for South Africa, the ISO, AS and a most probable number method were evaluated and compared. In addition, the effect of sample re-incubation with autochthonous amoebae on culture outcome was studied. Samples were collected from four environments, representing industrial water, mine water and biofilm. The samples were concentrated by membrane filtration and divided into three portions and cultured without pretreatment, after acid treatment and after heat treatment, on four culture media namely alphaBCYE, BMPA, MWY and GVPC agar. A selective approach, incorporating heat treatment, but not acid treatment, combined with culture on alphaBCYE and GVPC or MWY, was most appropriate for legionellae detection in the samples evaluated. Legionellae were cultured from 82% of the environmental samples we evaluated. In 54% of the samples tested, legionellae were present in numbers equal to or exceeding 10(2) colony-forming units per milliliter (cfu/ml). Legionella pneumophila serogroups (SGs) 1-14 were the most prevalent species and were present as single, or a combination of two or more SGs in a number of samples tested. Re-incubation of sample concentrates with autochthonous amoebae improved the culturability of legionellae in 50% of cultures on alphaBCYE and 25% on GVPC.

Molecular epidemiology of canid rabies in Zimbabwe and South Africa

The epidemiology of rabies in southern Africa is complex, due to a large number of vector species and the presence of at least two distinct biotypes of the virus. Our objective was to contribute to the understanding of the epidemiology of rabies in the southern African subcontinent by studying the genetic relationship of 89 rabies virus isolates from this region. In this study, we have focused on an analysis of viruses that cycle in canid host species (canid biotype) throughout South Africa and Zimbabwe. By phylogenetic analysis of the cytoplasmic domain of the glycoprotein and the non-coding G-L intergenic region, all the southern African canid viruses were found to be closely related and no apparent general distinction could be made between them. Although there was a minor degree of phylogenetic branching, with certain branches associated with cycles defined by species, location and time, the phylogenetic pattern indicated that canid rabies in southern Africa is derived from a single virus lineage, which has spread opportunistically within whatever canid host population is ecologically capable of sustaining prolonged cycles. This molecular epidemiological study presents the first comprehensive comparison of rabies viruses from South Africa and Zimbabwe and has demonstrated the need for multinational approaches towards the control of this important zoonotic disease in Africa.

Development of a diagnostic one-tube RT-PCR for the detection of Rift Valley fever virus

Diagnosis of Rift Valley fever (RVF) is based on serology and virus isolation. The disadvantages of the former include poor sensitivity, high cost, risks associated with using infectious virus as antigen, the lengthy duration of ELISA as well as cross-reactivity with other Phleboviruses. We developed, optimised and evaluated a one-tube reverse-transcription-polymerase chain reaction (RT-PCR) for the detection of Rift Valley fever virus (RVFV) in ruminants. The PCR primers for this assay were designed to anneal to a region within the M segment of the virus genome, encoding glycoproteins G1 and G2. A PCR amplicon of 363 bp was obtained. The sensitivity of the assay was determined to be 0.25 TCID50. This test should allow for the early and rapid detection of RVFV in both serum and whole blood. In addition, it could facilitate the quantification of antigen for the manufacture of current vaccines.

The 3A non-structural-protein coding region of the southern African SAT type isolates differs from that of other foot-and-mouth disease viruses

The 3A non-structural protein of foot-and-mouth disease viruses is a relatively conserved protein comprising 153 amino acids. Recent studies have demonstrated correlation between mutations in the 3A non-structural-protein-coding region, including a 10-amino acid deletion, and attenuation of the viruses in cattle. Although the 3A coding region of several type A, O and C isolates has previously been described, nucleotide sequence data of the 3A coding region of the South African Types (SAT) 1, 2 and 3 viruses are limited. Therefore, the 3A non-structural-coding region of different SAT serotypes was determined, analysed and compared to that of European, South American and Asian isolates. The 3A regions of the SAT isolates investigated differed markedly from that of types A, O, C and Asia-1, but were similar within the group.

Genetic heterogeneity of SAT-1 type foot-and-mouth disease viruses in southern Africa

Genetic relationships of 50 SAT-1 type foot-and-mouth disease viruses were determined by phylogenetic analysis of an homologous 417 nucleotide region encoding the C-terminal half of the VP1 gene and part of the 2A segment. Viruses obtained from persistently-infected African buffalo populations were selected in order to assess the regional genetic variation within the host species and compared with ten viruses recovered from recent and historical cases of clinical infection. Phylogenetic reconstructions identified three independently evolving buffalo virus lineages within southern Africa, that correspond with the following discrete geographic localities: (1) South Africa and southern Zimbabwe, (2) Namibia, Botswana and western Zimbabwe, and (3) Zambia, Malawi and northern Zimbabwe. This strict geographic grouping of viruses derived from buffalo was shown to be useful for determining the origin of recent SAT-1 epizootics in livestock. The percentage of conserved amino acid sites across the 50 SAT-1 viruses compared in this study was 50%. Most mutations were clustered within three discrete hypervariable regions, which coincide with the immunogenic G-H loop, H-1 loop and C-terminus region of the protein. Despite the high levels of variation within the primary sequence, secondary structural features appear to be conserved.

Characterization of major histocompatibility complex DRB diversity in the endemic South African antelope Damaliscus pygargus: a comparison in two subspecies with different demographic histories

Major histocompatibility complex (MHC) class II locus DRB was investigated by single-strand conformation polymorphism analysis (SSCP) and sequence analysis in the endemic South African antelope, Damaliscus pygargus, of which there are two subspecies. Greater polymorphism was found in the blesbok (D. p. phillipsi) subspecies (n = 44; 22 alleles) than in the bontebok (D. p. pygargus) subspecies (n = 45; 6 alleles). Erosion of allelic diversity in bontebok was most likely the result of two severe bottleneck events caused by hunting pressure and parasitic infection. A majority of the polymorphism observed was found within the peptide binding region (PBR) where dN/dS ratios were higher than for the non-PBR region. This, and the apparent trans-species relationship among alleles in a bovid phylogeny, suggest the evolution of diversity by heterosis or frequency-dependent selection.

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.

Characterization of the structural-protein-coding region of SAT 2 type foot-and-mouth disease virus

The South African Territories (SAT) types of foot-and-mouth disease (FMD) virus show marked genomic and antigenic variation in sub-Saharan Africa that is to a large extent geographically determined. This has implications for selection of appropriate vaccine strains as well as the accuracy of laboratory diagnosis. However, adaptation of field isolates as vaccine strains is cumbersome, time consuming and expensive. We propose the construction of recombinant viruses in which specific antigenic determinants can be manipulated. To achieve this goal, the structural-protein-coding region of a SAT 2 vaccine strain, ZIM 7/83/2, was determined and compared with two other known SAT 2 P1 regions. Five hypervariable regions were identified of which four are situated within VP1. The cleavage sites for proteolytic processing differs from serotype A, while the junction between P1/2A is variable within the SAT 2 serotype. These differences could influence the construction of recombinant vaccines.

A nucleotide-specific polymerase chain reaction assay to differentiate rabies virus biotypes in South Africa

Antigenic and nucleotide sequence analyses have shown that two distinct biotypes of rabies virus are circulating in South Africa. One of these typically infects members of the family Canidae, while the other comprises a heterogeneous group of apparently indigenous viruses, infecting members of the Viverridae family. In recent times, it has become evident that a considerable amount of cross-infection may occur and the manifestation of viverrid rabies in non-viverrid animals in particular appears to have become more commonplace. Consequently, the need to rapidly distinguish between rabies virus biotypes has become increasingly important in efforts to monitor the epidemiology of rabies in the southern African region. In this study, a nested polymerase chain reaction (PCR) assay was developed to distinguish between these two groups of rabies viruses. Consensus oligonucleotides were used to amplify the cytoplasmic domain of the rabies virus glycoprotein and the adjacent intergenic region. The resultant amplicon was subsequently used as template in second round heminested PCR in the presence of type-specific primers, thereby successfully generating amplicons of characteristic size for each biotype.

Removal of waterborne human enteric viruses and coliphages with oxidized coal

Human enteric viruses and coliphages have been detected in water that has undergone what is generally considered adequate treatment, including chlorination. Because small numbers of virus particles are needed for the initiation of a productive virus infection, the presence of any number of virus particles in water resources will always be of concern. In this investigation the ability of oxidized coal to remove viruses from water was investigated. The oxicoal product was found to be able to remove not only coliphages, but also various pathogenic human viruses from seeded water sources. Removal was dependent upon the type of virus, the period of exposure, and the concentration of oxidized coal.

Characterization of the Crater Disease Strain of Rhizoctonia solani

ABSTRACT Crater disease (CD) of wheat is caused by a Rhizoctonia solani strain of ambiguous phylogeny. Anastomosis reactions confirmed placement of CD-causing R. solani in anastomosis group (AG) 6, with results indicating a closer affinity to AG-6 GV than to AG-6 HG. Cultures of CD isolates were initially white to cream, turning a yellowish light brown after 10 days. Concentric rings of dark and light mycelium were evident from an early stage. Mycelium generally was appressed to the agar surface, with sparse aerial growth. A few light-colored, irregularly shaped sclerotia could be discerned after 2 weeks. The mean hyphal diameter of CD-causing R. solani was 7.46 mum (ranging from 5.0 to 10.0 mum), and cells contained a mean number of four (ranging from two to eight) nuclei, compared to a mean hyphal diameter of 8.58 and 8.42 mum and a mean nuclear number of six and four for AG-6 HG and AG-6 GV, respectively. The CD isolates had a slower growth rate (15.3 mm/day) than AG-6 HG (29.1 mm/day) and AG-6 GV (22.6 mm/day) but, like AG-6, were thiamine prototrophic. Conspicuous nodulose swellings were produced by CD-causing R. solani on roots of wheat, and infection resulted in retarded shoot growth. Smaller nodules were evident on bean and soybean roots. Fingerprint patterns generated for the various isolates with four enzymes, HpaII, Sau3AI, TaqI, and CfoI, showed the presence of a unique 610-bp fragment in the pathogen. It is proposed that CD-causing R. solani isolates represent a distinct intersterility group within AG-6 that is more related to subgroup GV than to subgroup HG.

Stable protein-RNA interaction involves the terminal domains of bluetongue virus mRNA, but not the terminally conserved sequences

The interaction of bluetongue virus (BTV) proteins with viral RNA was investigated in vitro by means of a biochemical approach. By subjecting cytoplasmic extracts from virus-infected baby hamster kidney cells and in vitro synthesized radiolabeled RNA to ultraviolet cross-linking assays, we demonstrated that, of all the BTV proteins, NS2 becomes most intimately associated with the labeled viral RNA. Competition binding studies indicated that NS2 has the greatest affinity for the 3' region of the viral transcripts. By analyzing the binding efficiency of NS2 to mutant RNA transcripts which lacked the fully conserved 5'- and/or 3'-terminal hexanucleotides, we have established that these sequences are not necessary for optimal binding. The specificity of the NS2-RNA interaction was investigated by competition experiments with unlabeled BTV-specific homologous and heterologous competitor RNAs as well as with viral double-stranded RNA (dsRNA). Although apparent differences in the ability of NS2 to bind to the different RNA transcripts were observed, it did not bind to the dsRNA.

Comparative sequence analysis and expression of the M6 gene, encoding the outer capsid protein VP5, of African horsesickness virus serotype nine

The entire nucleotide and deduced amino acid sequence of the M6 gene of African horsesickness virus (AHSV) serotype nine has been determined from four overlapping cDNA clones. The gene was found to be 1566 bp long, encoding a protein of 505 amino acids with a molecular weight of 56 737 Da and a nett charge of - 1 at neutral pH Comparative sequence analysis of the deduced amino acid sequence with the VP5 protein of AHSV-4, showed that only 81% of amino acids were conserved in type and position, although alternating regions of lower and higher conservation was identified by alignment of the primary sequences of different orbiviral VP5 proteins. Antigenically authentic AHSV-9 VP5 was also expressed in a baculovirus expression system and the expressed protein was shown to react specifically with anti-AHSV-9 as well as AHSV-3 serum in Western blot analysis.

Site-specific mutations in the NS2 protein of epizootic haemorrhagic disease virus markedly affect the formation of cytoplasmic inclusion bodies

The importance of a conserved amino acid motif in the nonstructural protein NS2 of different orbiviruses was investigated with regard to virus inclusion body (VIB) formation. A number of epizootic haemorrhagic disease virus NS2 deletion and substitution mutants were prepared and expressed as baculovirus recombinants. Deletion of the motif or substitution of at least three residues within the region, had a detrimental effect on VIB formation in insect cells. Furthermore, these NS2 mutants were not complexed with single-stranded RNA in infected cells and appeared to be cytotoxic. Cumulatively, the results suggest that this motif is an essential structural determinant for NS2 function.

Identification of a short domain within the non-structural protein NS2 of epizootic haemorrhagic disease virus that is important for single strand RNA-binding activity

The role that a conserved amino acid motif, found in the non-structural protein NS2 of orbiviruses, plays in the interaction of this protein with single stranded (ss) RNA was investigated by mutation analysis of the NS2 of epizootic haemorrhagic disease virus. An NS2 mutant in which this motif (amino acids 75 to 83) was deleted was expressed in Spodoptera frugiperda cells by a recombinant baculovirus and found to be unable to bind to poly(U)-Sepharose. The deletion mutant also differed from wild-type NS2 in that it did not appear to be complexed with ssRNA in cells infected with the baculovirus recombinant. Furthermore, the deletion exerted an adverse effect on the ability of NS2 to form inclusion bodies in the cytoplasm of baculovirus-infected insect cells. To further characterize the role of this motif in RNA-binding, specific residues within the region were substituted by site-directed mutagenesis and the mutants were expressed in Escherichia coli as fusion proteins. Analysis of the different mutant proteins indicated that in each case ssRNA-binding was impaired relative to that of the wild-type NS2 control. The degree of impairment corresponded to the number of amino acid substitutions and the largest effects were associated with non-conserved substitutions. It is suggested that the conserved motif is an important structural determinant in the interaction of NS2 with ssRNA.

Molecular epidemiology of rabies virus in South Africa: evidence for two distinct virus groups

In order to derive phylogenetic relationships between rabies virus isolates from different geographical locations and host species in South Africa, two genome regions of the virus, viz. the cytoplasmic domain of the glycoprotein and the G-L intergenic region (pseudogene), were sequenced. A high level of nucleic acid sequence conservation indicated a close phylogenetic relationship between virus isolates from domestic dogs, jackals and bat-eared foxes, i.e. Canidae. These isolates appeared to be distinct from but closely related to European strains of rabies virus. However, a phylogenetically distinguishable and distant group, which contained isolates from mongooses (i.e. Viverridae) was identifiable. The latter group appears to be distantly related to European and vaccine strains of rabies virus and may have evolved uniquely on the central plateau of South Africa. Our data also indicate that spillover from mongooses (or other viverrids) to canid hosts occurs occasionally.

Comparison of the expression and phosphorylation of the non-structural protein NS2 of three different orbiviruses: evidence for the involvement of an ubiquitous cellular kinase

The non-structural protein NS2 of epizootic haemorrhagic disease (EHD), bluetongue (BT) and African horsesickness (AHS) viruses has each been expressed to high levels using a baculovirus vector gene expression system. It was found that the recombinant baculovirus-expressed EHDV NS2 protein was resolved as a doublet following PAGE. Peptide mapping of these protein bands indicated that they were identical. The difference in the sizes of the NS2 protein bands could not be attributed to the phosphorylation of NS2 or other posttranslational modification such as N-glycosylation and remains obscure. The EHDV, BTV and AHSV baculovirus-expressed NS2 proteins were all phosphorylated in vitro without the addition of an exogenous kinase. An unphosphorylated form of EHDV NS2, obtained by expressing the NS2 gene as a fusion protein in Escherichia coli cells, could be phosphorylated in vitro by a protein kinase associated with the cytoplasm of insect cells. The phosphorylated version of this protein was found to be significantly less efficient in binding ssRNA, compared to the unphosphorylated version.

Molecular epidemiology of rabies virus in South Africa

Nucleic acid sequence analysis was used to determine the phylogenetic relationships amongst rabies viruses isolated from typical canid hosts such as bat-eared fox, jackal and dog in South Africa (SA). Geographical factors were taken into account in the selection of isolates and three different regions within the genomes of the isolates were compared for their use as phylogenetic indicators. The three genome regions, being the cytoplasmic domain of the G-gene, the G-L intergenic pseudogene and the antigenic domain II of the N-gene were found to differ in terms of the of nucleic acid conservation, but produced similar results when analyzed phylogenetically. The SA canid isolates were found to be closely related and could clearly be distinguished from all other rabies virus groups for which sequence data is available. In addition four SA mongoose rabies isolates were studied which were shown to be distant from the SA canid rabies virus group as well as from any other rabies viruses (or group) for which sequence data is available. Our results also indicate that spillover between the distinct canid and viverrid host reservoirs may occur.

A comparison of the nucleotide sequences of cognate NS2 genes of three different orbiviruses

The genes encoding nonstructural protein NS2 of African horsesickness virus (AHSV) and epizootic hemorrhagic disease virus (EHDV) were cloned, sequenced, and compared to the NS2 gene of bluetongue virus (BTV). Nucleotide similarity ranged from 53 to 60%. The length of the proteins varied from 376 amino acids (EHDV) to 365 amino acids (AHSV). The N-terminal half of NS2 is more conserved (+/- 58% similarity) among the three orbiviruses, while the C-terminal half contains a 120 amino acid region of low similarity (18%). The variable region has a high content of alpha-helix conformation and a hydrophilic character. A short region of 9 amino acids contains 5 amino acids that are either similar or identical in single-stranded RNA binding proteins of BTV, EHDV, AHSV, reovirus and rotavirus.

A comparison of different genomic probes in the detection of virus-specified RNA in Orbivirus-infected cells

Different 32P-labelled genomic probes of bluetongue virus (BTV), epizootic haemorrhagic disease virus (EHDV) and equine encephalosis virus (EEV) were compared with respect to the detection of virus-specified RNA in infected cells. The probe derived from the genome segment that encodes nonstructural protein NS1 was found to be the most sensitive, detecting virus-specified RNA in glutaraldehyde-fixed cells as early as 2-3 h p.i. This comparison was based on the observation that the NS1 gene probe required a smaller number of infected cells to produce a positive hybridization signal than the other nucleic acid probes. The only exception was the EHDV NS2 gene probe which appeared to be as sensitive as the NS1 gene probe. The advantage of using the NS1 gene probe was particularly evident in the analysis of cells infected at very low multiplicities of infection. At a multiplicity of infection of 1 x 10(-5) plaque forming units/cell, virus-specified RNA could be detected 48 h after infection. The greater sensitivity of the NS1 gene-specific probe is ascribed to the fact that its target, the NS1 mRNA, is transcribed more frequently than the other target viral mRNAs. The major application of the cell-hybridization method is the rapid detection of small quantities of infectious virus particles.

Synthesis of the virus-specified tubules of epizootic haemorrhagic disease virus using a baculovirus expression system

The formation of virus-specific tubules is one of the most characteristic features in the orbivirus infection cycle, yet little is known about their role in virus replication. The tubuli are composed of a major nonstructural protein, NS1. We have investigated the expression of the NS1-encoding gene of epizootic haemorrhagic disease virus serotype 2 (Alberta-strain) by producing a recombinant Autographa californica nuclear polyhedrosis virus (AcNPV). Prior to cloning in the baculovirus transfer vector, pAcYM1 and cotransfection with AcNPV DNA, the NS1 gene was tailored by means of a polymerase chain reaction method to remove G/C tails. The baculovirus recombinant, AcNPV-EHDV2 NS1, expressed large amounts of a 55 K protein which could be purified by sucrose gradient sedimentation as a tubular complex. It appeared that the tubules could break up into 50 nm diameter circular units, which in turn were composed of approximately 16 subunits. The circular units appeared to be hollow and stacked on top of one another (100 units/micron tubule length), giving the tubules a segmented, ladderlike appearance. A large excess of EHDV2-specific tubuli could also be demonstrated in AcNPV-EHDV2 NS1-infected Spodoptera frugiperda cells by electron microscopic examination of thin sections. With pulse-labelling experiments it was shown that, regardless of the level of NS1 expression, the majority of NS1 synthesized in a 30 min period could only be recovered in a particulate form.

A characterization of the nonstructural protein from which the virus-specified tubules in epizootic haemorrhagic disease virus-infected cells are composed

The complete nucleotide sequence of segment 6 of epizootic haemorrhagic disease virus serotype 2 (Alberta) which encodes nonstructural protein NS1 was determined from a cDNA clone containing a full-length copy of the gene. The gene was found to be 1806 bp in length, constituted by one open reading frame of 1656 bp which is flanked by 5' and 3' noncoding regions of 32 and 118 bp, respectively. The conserved 5' and 3' terminal hexanucleotide sequences were identical to those of BTV-10. The 5' noncoding nucleotide sequences of cognate genome segments 4, 6 and 8 were found to be highly conserved in EHDV-2 and BTV-10. The 3' noncoding regions are less conserved but share common characteristics. The predicted EHDV-2 NS1 gene product, a 552 amino acid polypeptide, is predominantly hydrophobic and has a net charge of +5 at neutral pH. Comparison to its BTV-10 counterpart revealed a high degree of homology. Regions of high amino acid similarity were shown to correlate with hydrophobic domains on the proteins whilst regions of lower amino acid similarity corresponded with the hydrophilic domains. Thirteen conserved cysteine residues of which the majority occurred in hydrophobic regions with more than 80% amino acid similarity were identified.

A comparison of different cloned genome segments of epizootic haemorrhagic disease virus as serogroup-specific probes

The eight largest double-stranded (ds) RNA genome segments of epizootic haemorrhagic disease virus (EHDV) serotype 2 (Alberta strain) have been cloned. Of these, segments 4, 5, 6, 7, and 8 are represented by clones that correspond in size to those predicted for full-length clones. The different clones were used as nucleic acid probes to study the nucleic acid homology of cognate genes of four different EHDV serotypes. The results indicated that the 4 isolates may be subdivided in two geographic groups which include Ibaraki virus as the sole member of one group and EHDV1 (New Jersey), EHDV2 (Alberta) and EHDV6 (XBM 67--isolated in South Africa) as a second. Genome segments 1, 3, 4, 6, and 8 were found to be highly conserved with more than 90% homology amongst cognate genes of three of the members of the EHDV serogroup. Of these, segments 1 and 3 showed the largest degree of homology with cognate genes of members of the BTV serogroup. Segment 6 and 8 probes of EHDV2 (Alberta) on the other hand did not hybridize with BTV dsRNA under conditions of moderate to low stringency and are recommended for use as EHDV group-specific probes.