Evaluation of infectivity and transmission of different Asian foot-and-mouth disease viruses in swine

Most isolates of foot-and-mouth disease virus (FMDV) display a broad host range. Since the late 1990s, the genetic lineage of PanAsia topotype FMDV serotype O has caused epidemics in the Far East, Africa, the United Kingdom, France, the Netherlands, and numerous other countries throughout Europe and Asia. In contrast, there are several FMDV isolates that exhibit a more restricted host range. A Cathay topotype isolate of FMDV serotype O from the 1997 epizootic in Taiwan (O/TAW/97) demonstrated restricted host specificity, only infecting swine. Methods used to evaluate infectivity and pathogenicity of FMDV isolates in cattle are well-documented, but there has been less progress studying transmission and pathogenicity of FMDV isolates in pigs. In previous studies designed to examine pathogenicity, various chimeric viruses derived from O/TAW/97 were intradermally inoculated in the heel bulb of pigs. Subsequent quantitative scoring of disease and evaluation of virus released into nasal secretions and blood was assessed. Here we prove the usefulness of this method in direct and contact inoculated pigs to evaluate infectivity, pathogenicity and transmission of different Asian FMDV isolates. Virus strains within the Cathay topotype were highly virulent in swine producing a synchronous disease in inoculated animals and were efficiently spread to in-contact naive pigs, while virus strains from the PanAsia topotype displayed more heterogeneous properties.     

云南边境O型口蹄疫监测及病毒VP1基因序列分析

口蹄疫是由口蹄疫病毒引起的主要侵袭偶蹄动物的一种急性热性高度接触性传染病。口蹄疫病毒为微RNA病毒科口蹄疫病毒属成员,存在7个不同血清型,病毒VP1蛋白抗原性差异是病毒血清型划分依据,而其编码基因(1D)核苷酸序列差异是同型病毒拓扑型(Topotype)或基因型鉴别依据。采用O/A/C/Asia-1多重RT-PCR技术,对2006年自云南边境地区采集的120份动物组织样品,进行口蹄疫病原监测,检出O型口蹄疫病毒阳性样品15份。对阳性样品中病毒VP1基因全序列进行扩增、纯化后,克隆至pMD18-T载体测序,并与已知代表性毒株进行比对及系统发育分析。结果发现:云南边境O型口蹄疫病毒阳性样品VP1基因核苷酸序列同源性介于77.3%~98.7%,可划分为3个不同的拓扑型或基因型:中东-南亚型(ME-SA)或泛亚型(PAN-Asia)、古典中国型(Cathay)、东南亚型(SEA)。部分样品VP1蛋白表位43位、154位关键性氨基酸位点存在变异。     

Molecular epidemiology of foot-and-mouth disease virus type A in South America

A databank of 78 VP(1) complete sequences of type A foot-and-mouth disease virus (FMDV) from South American isolates was constructed. Forty-nine samples corresponded to FMDV that circulated between the years 1999-2008, mainly in Venezuela, where most type A outbreaks have occurred lately and twenty-nine to strains historically relevant for the continent. The phylogenetic analysis showed that all South American FMDV belonged to the Euro-SA topotype. Sixteen subgenotypes could be identified, based on a 15% nucleotide divergence cut-off criterion: eight are extinguished, three were active until the year 2002 and the remaining five circulated in Venezuela during the years 2001-2007, illustrating the potential for FMDV diversification under appropriate selective pressure. The last emergencies reported in already-free areas of Colombia in 2004 and 2008 were closely related to isolates acting in Venzuela. Evidence of positive selection over codon 170, within the immunogenic site 4 of VP1 protein, was recorded. A codon deletion in amino acid position 142, within the G-H loop, was found in some isolates within subgenotypes 14, 15 and 16. Conversely amino acid deletion 197 was restricted to all isolates within a particular genetic cluster. The present work is the first comprehensive phylogenetic analysis of FMDV type A in South America, filling a gap of knowledge with respect to both, historical and acting viruses. The results provided evidence that supports the ecosystem dynamics in the region, and also served as an input to establish genetic links of emergencies in already-declared free areas, highlighting the need for strengthening control activities.     

Phylogenetic analysis of the erythrocytic Anaplasma species based on 16S rDNA and GroEL (HSP60) sequences of A. marginale,A. centrale,and A. ovis and the specific detection of A. centrale vaccine strain

Phenotypic criteria for the identification of erythrocytic ruminant Anaplasma species has relied on subjective identification methods such as host pathogenicity (virulence for cattle or sheep) and/or the location of Anaplasma inclusion bodies within the host's red cells. Sequence comparisons of new and available GenBank Accessions were investigated to elucidate the relationships among these closely related Anaplasma species. Twenty-one 16S rDNA and GroEL (HSP60) sequences from 13 Anaplasma marginale (South Africa, Namibia, Zimbabwe, Israel, USA, Australia and Uruguay), three A. centrale (South Africa and Japan), two A. ovis (USA and South Africa), and two unknown Anaplasma species isolated from wild ruminants (South Africa), were compared. 16S rDNA maximum-likelihood and distance trees separated all A. marginale (and the two wild ruminant isolates) from the two South African A. centrale (including original vaccine strain, Theiler, 1911). The Japanese A. centrale (Aomori) demonstrated the lowest sequence identity to the remaining erythrocytic Anaplasma species. A. ovis inter-species relationships could not be resolved through the 16S rDNA analyses, whereas strong bootstrap branch support is demonstrated in the GroEL distance tree using A. ovis OVI strain. All erythrocytic Anaplasma species and isolates were confirmed to belong to the same cluster showing strong branch support to Anaplasma (Ehrlichia) phagocytophilum with Ehrlichia (Cowdria) ruminantium and Rickettsia rickettsii serving as appropriate out-groups. Based on groEL sequences, a specific PCR method was developed which amplified A. centrale vaccine (Theiler, 1911) specifically. This study confirms the suitability of 16S rDNA sequences to define genera and demonstrates the usefulness of GroEL sequences for defining species of erythrocytic Anaplasma.     

Evolutionary trend of foot-and-mouth disease virus in Hong Kong

Foot-and-mouth disease is an endemic animal disease in Hong Kong. In this study, a total of 70 clinical specimens were collected from locally infected pigs from 2001 to 2010. Phylogenetic analysis of VP1 sequences reveal that all Hong Kong FMDV serotype O isolates are classified into three lineages: HK-A and HK-B in Cathay topotype, and HK-C in SEA topotype. Regression analysis projects that the time of divergence from the most recent common ancestor of HK-A and HK-B are 1964 ± 12 and 1987 ± 9 years respectively. Although HK-B shares a common ancestor with strains that caused outbreak in Taiwan and Philippines, there is no consolidated evidence demonstrating the order of introduction events among these regions. HK-C lineage is the latest FMDV isolated in Hong Kong. This virus is likely adopted from bovine into porcine. As local pigs confer immunity mainly against Cathay topotype viruses, introduction of HK-C viruses have led into an unexpectedly high severity and rapid spreading rate of the disease. A systematic surveillance and communication network is essential to provide accurate information in controlling the pandemics.     

Study of the genetic heterogeneity of SAT-2 foot-and-mouth disease virus in sub-Saharan Africa with specific focus on East Africa

The epidemiology of serotype SAT-2 foot-and-mouth disease was investigated in sub-Saharan Africa by phylogenetic analysis using the 1D gene encoding the major antigenic determinant. Fourteen genotypes were identified of which three are novel and belong to East Africa, bringing the total number of genotypes for that region to eight. The genotypes clustered into three lineages that demonstrated surprising links between East, southern and south-western Africa. One lineage was unique to West Africa. These results established numerous incursions across country borders in East Africa and long term conservation of sequences for periods up to 41 years. Ethiopia, Kenya and Uganda have all experienced outbreaks from more than one unrelated strain, demonstrating the potential for new introductions. The amount of variation observed within this serotype nearly equalled that which was found between serotypes; this has severe implications for disease control using vaccination.     

Sequence analysis of the protein-coding regions of foot-and-mouth disease virus O/HK/2001

The nucleotide sequence of the protein-coding region of foot-mouth-disease virus (FMDV) strain O/HK/2001 was determined and compared with the sequences of other FMDVs that were registered in GenBank. The protein-coding region was 6966 nucleotides in length and encoded a protein of 2322 amino acid residues. Comparison of the nucleotide sequence and its deduced amino acid sequence with those of other isolates indicated that O/HK/2001 belonged to the Cathay topotype. A genomic coding region nucleotide sequence phylogenetic tree of several FMDV-O isolates showed that O/HK/2001 was most closely related to FMDV isolates found in Taiwan during 1997, and especially shared significant similarity to HKN/2002, suggesting that the virus causing outbreaks in Hong Kong was genetically most-closely related to that causing an outbreak of type O in Taiwan. Mutations in O/HK/2001 were revealed, including frequent substitutions in the VP1 and L proteins, and deletions involving 10 amino acid residues in the 3A protein. This study was undertaken to assess the regional variation of prevalent FMDV type O viruses and to establish a sequence database for FMDV molecular epidemiological investigation.     

非洲奶业发展现状及中非合作潜力研究

奶业是非洲居民重要的收入和就业来源,是重要的农业产业。2018年,非洲奶业生产总值171.22 亿美元,占畜牧业总产值的24.0%;奶牛存栏6 752.49 万头,主要集中在东非、北非和西非地区,养殖方式以散养为主,平均存栏仅3 头,部分品种仍以役用为主,牛奶生产仅是副产品,平均单产512.8 kg/头·年,年生鲜乳产量3 462.85 万t;埃及、肯尼亚和南非是主要的乳制品加工国家,加工量占非洲生鲜乳产量的近30%;2019年乳制品消费量折合生鲜乳为5 468.21 万t,鲜奶是最主要的消费品类,占60%以上,其次是奶粉和奶酪,分别占消费量（折合生鲜乳）的16%和15%,人均消费量有所下降,2019年为41.74 kg/人·年;乳制品贸易长期处于净进口趋势,2018年进口量198.72 万t,进口额48.57 亿美元,北非、西非和东非是主要进口地区。非洲奶牛养殖提升空间巨大,乳制品加工前景广阔,乳制品消费增长空间巨大,中国进一步加强与非洲奶业在奶牛养殖、乳制品加工以及奶业贸易等方面的国际合作,推动奶业走出去。     

Review of African swine fever outbreaks history in South Africa: From 1926 to 2018

The article reviews the outbreaks and distribution of African swine fever (ASF) in South Africa since the first probable outbreak that occurred in the Koedoesrand Ward in 1926. Retrospective data on the ASF outbreaks in South Africa were obtained from the World Organisation for Animal Health (OIE) disease database and the South African veterinary services annual reports in addition to published articles and online sources. South Africa has experienced many outbreaks that can be divided into 2 time periods: the period before the development of the OIE diseases database (1993) and the period after. More than 141 outbreaks of ASF were reported during the first period. Since the development of OIE disease database, 72 outbreaks directly involving 2968 cases, 2187 dead and 2358 killed pigs mainly in smallholder pig farms were reported. The median number of cases for a given ASF outbreak is 17, but in 50% of outbreaks no pigs were killed for prevention. The most important ASF outbreak was reported in April 2014 in the Greater Zeerust district (North West province) involving 326 cases and 1462 killed pigs. However, the outbreak with highest mortality involving 250 pigs was reported in 2016 (Free State province). According to phylogenetic analysis, nine p72 genotypes (I, III, IV, VII, VIII, XIX, XX, XXI and XXII) have been identified in South Africa. Season-wise, more outbreaks were recorded during summer. It was also observed that the OIE disease database could contain errors that would have been introduced through compiled forms at country level. Spatiotemporal studies on ASF outbreaks in South Africa are therefore required in order to assess statistically and quantitatively the clustering of outbreaks over space and time.     

A status report of veterinary education in Ethiopia: perceived needs, past history, recent changes, and current and future concerns

Ethiopia, which owns the most important livestock resources in Africa, opened its first faculty of veterinary medicine in 1979. In 2003, in response to a government mandate to increase the number of veterinarians, four new veterinary faculties were founded, but these facilities still have very limited resources. Currently, quality standards and controls for veterinary studies are not established in Ethiopia, and the country does not have any type of veterinary council or oversight body to establish such standards or the essential evaluation and credentialing procedures. The veterinary degree, as currently obtained in Ethiopia, is not internationally recognized. A second specific concern for veterinary education in Ethiopia is that it is not well adapted to the special needs of the country. Clearly, quality control of veterinary education needs to be established, and teaching methods and materials need to be adapted to the special needs of the country. So far, the veterinary faculty in Ethiopia has been more interested in partnerships with universities from developed countries than in partnerships and cooperation with other African universities. In 2002, after six years of cooperation with a German university, the Veterinary Faculty at Addis Ababa started its own post-graduate program, with some key contributions from foreign instructors and some foreign funding. While this has been a service to Ethiopian veterinary medicine, the cooperation of the Ethiopian veterinary schools with African universities must also be strengthened. Overall, the good efforts to date in Ethiopian veterinary medicine have only barely scratched the surface of its critical needs. In order to meet Ethiopia's needs for both a reliable and high-quality veterinary education and a trustworthy animal disease surveillance mechanism, it is important that veterinary education in Ethiopia be improved.     

Four p67 alleles identified in South African Theileria parva field samples

Previous studies characterizing the Theileria parva p67 gene in East Africa revealed two alleles. Cattle-derived isolates associated with East Coast fever (ECF) have a 129 bp deletion in the central region of the p67 gene (allele 1), compared to buffalo-derived isolates with no deletion (allele 2). In South Africa, Corridor disease outbreaks occur if there is contact between infected buffalo and susceptible cattle in the presence of vector ticks. Although ECF was introduced into South Africa in the early 20th century, it has been eradicated and it is thought that there has been no cattle to cattle transmission of T. parva since. The variable region of the p67 gene was amplified and the gene sequences analyzed to characterize South African T. parva parasites that occur in buffalo, in cattle from farms where Corridor disease outbreaks were diagnosed and in experimentally infected cattle. Four p67 alleles were identified, including alleles 1 and 2 previously detected in East African cattle and buffalo, respectively, as well as two novel alleles, one with a different 174 bp deletion (allele 3), the other with a similar sequence to allele 3 but with no deletion (allele 4). Sequence variants of allele 1 were obtained from field samples originating from both cattle and buffalo. Allele 1 was also obtained from a bovine that tested T. parva positive from a farm near Ladysmith in the KwaZulu-Natal Province. East Coast fever was not diagnosed on this farm, but the p67 sequence was identical to that of T. parva Muguga, an isolate that causes ECF in Kenya. Variants of allele 2 were obtained from all T. parva samples from both buffalo and cattle, except Lad 10 and Zam 5. Phylogenetic analysis revealed that alleles 3 and 4 are monophyletic and diverged early from the other alleles. These novel alleles were not identified from South African field samples collected from cattle; however allele 3, with a p67 sequence identical to those obtained in South African field samples from buffalo, was obtained from a Zambian field isolate of a naturally infected bovine diagnosed with ECF. The p67 genetic profiles appear to be more complex than previously thought and cannot be used to distinguish between cattle- and buffalo-derived T. parva isolates in South Africa. The significance of the different p67 alleles, particularly the novel variants, in the epidemiology of theileriosis in South Africa still needs to be determined.     

Susceptibility of buffaloes, cattle and goats to infection with different stocks of Trypanosoma vivax transmitted by Glossina morsitans centralis

A comparison was made of the susceptibility of buffaloes, cattle and goats to infection with Trypanosoma vivax transmitted either by Glossina morsitans centralis or by syringe inoculation. Three different isolates of T vivax (two from East Africa, one from West Africa) were used to compare skin reactions, parasitaemia, anaemia and the development of trypanosome-specific antibodies in buffaloes, cattle and goats. African buffaloes reared in captivity in an area free from trypanosomiasis proved to be highly resistant to infection with the three stocks of T vivax tested, irrespective of whether infection was by tsetse transmitted metacyclic forms or by intradermal or intravenous inoculation of bloodstream forms of the parasite. The bites of 19 tsetse infected with a West African T vivax stock did not cause local skin reactions, detectable bloodstream infections or antibody responses in two buffaloes. Following the bites of 120 tsetse flies infected with the same stock, two different buffaloes showed no local skin reactions, but had detectable bloodstream infections without showing signs of anaemia. Cattle and goats infected in a similar way showed severe local inflammatory skin reactions, high levels of parasitaemia and severe anaemia. The two East African stocks of T vivax caused no local skin reactions and only a transient parasitaemia in buffaloes following tsetse-transmitted infection or intradermal inoculation of bloodstream forms. On the other hand, cattle and goats infected with the East African stocks showed high parasitaemias but local skin reactions only occurred in the goats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evolution of Acoustic Behaviour in African Bufo (Anura: Bufonidae)

Mating calls are known for 29 species of African Bufo belonging to 11 species groups. Twenty-five African species, representing eight species groups (including four groups or complexes having 2N=22) have calls which Martin (1972) termed Type I. This call type is also found in Schismaderma carens, Nectophrynoides tornieri and N. occidentalis. It is known in only four species of Bufo outside Africa and in Odontophrynus americanus which is thought to be closely related to leptodactylids that gave rise to the genus Bufo. Four African species of Bufo have Type II calls.

Geographic distribution of three call types indicates large radiations of one or two call types in South America, North America and Africa. The European and Asian Bufo faunas appear to be derived primarily from American radiations.

The radiation of bufonids in Africa appears to be equal to that of South America. An explanation of this may be that Bufo or its progenitor evolved prior to the continental separation of South America and Africa.     

Molecular characterization of Ethiopian indigenous goat populations

Six Ethiopian indigenous goat populations viz. Gumuz, Agew, Begia-Medir, Bati, Abergelle, and Central Abergelle were genotyped for 15 microsatellite markers recommended by Food and Agriculture Organization of the United Nations and International Society for Animal Genetics. A total of 158 individual goats were tested to assess genetic variations within and between the goat populations in the Amhara Region of Ethiopia. The markers revealed 100% polymorphism across six goat populations indicating the presence of genetic diversity, which is an important variable to measure genetic variability within and between populations. The mean observed and expected heterozygosity values ranged from 0.56 (Central Abergelle) to 0.68 (Bati) and 0.59 (Abergelle) to 0.69 (Agew goat), respectively. The lowest genetic distance was observed between Begia-Medir and Central Abergelle (0.039), and the largest distances between Agew and Abergelle (0.140) and Gumuz and Abergelle (0.169). Neighbor-joining and the unweighted pair group method with arithmetic mean methods with bootstrap value of 1,000 was used which grouped the six goat populations into two major groups viz. the Abergelle goat cluster as one group and the Agew, Gumuz, Bati, Begia-Medir, and Central Abergelle goats as the second group. In our study, the obtained higher total variation within the goat populations (95%) confirms a close relatedness of the studied goat ecotypes, which might have happened due to the existence of uncontrolled animal breeding strategies resulting from uncontrolled movement of animals through various market routes and agricultural extension systems. The study contributed to the genetic characterization of Ethiopian indigenous goat populations and demonstrated the usefulness of the 15 microsatellite makers for biodiversity studies in goats.     

Outbreak investigations and genetic characterization of foot-and-mouth disease virus in Ethiopia in 2008/2009

The study was conducted in three regional states of Ethiopia: Amhara, Oromia, and Addis Ababa from August 2008 to April 2009 with the objectives of identifying the genetic diversity of serotypes and topotypes in Ethiopia, and determining the attack rate and associations of potential risk factors with foot-and-mouth disease (FMD) seropositivity. A total of 496 cattle were clinically and serologically examined for presence of specific lesions and nonstructural protein for FMD, respectively. Of which, 140 (28.2%) manifested clinical signs and lesions suggestive of FMD, and 219 (44.2%) were seropositive. From a total of 7,781 animals observed and recorded on a designed format in six districts, 1,409 (19.6%) were infected, and 15 (0.12%) died during outbreaks of FMD. Epidemiological investigations revealed that the morbidity rate of the disease was 21.1% in Akaki-kality sub-city, but the mortality rate was <2% in all districts. Furthermore, the mortality and case fatality rates were relatively higher, 1.6% and 8.9% in calves than the other age groups, respectively. From a total of 33 bovine epithelial tissue-cultured samples, 19 (57.6%) showed CPE for FMD virus, in which 16 samples had serotype O and EA-3 topotype, while three samples had found serotype A, Africa topotype, and G-VII strain. Various strains of FMD viruses were isolated in Ethiopia in this study, and therefore, further detailed studies on the evaluation of available vaccines and the development of a vaccine which contains cocktails of antigens of FMD virus strains in the country should be encouraged.     

Molecular epidemiological investigation of foot-and-mouth disease virus in Korea in 2000

The genetic relatedness of 7 Korean type O field strains of foot-and-mouth disease virus (FMDV) in clinical specimens collected from 5 different geographic locations in 2000 was investigated. The sequence of 162 nucleotides (nt 478-639) at the 3' end of the 1D (VP1) genes was determined from amplified cDNA fragments, and subjected to the analysis for the sequence identity/divergence and phylogenetic relationship. The overall nucleotide sequence divergence among the 7 field strains was 0 to 3.8%, suggesting that they are closely related to each other. Phylogenetic analysis with the known Middle East-South Asia (ME-SA) topotype strains showed that the 7 Korean field strains formed two distinct clusters within the same lineage of the ME-SA topotype strains. Cluster 1 consisted of the strains of the primary foci of infection (Paju and Hongseong), and closely related to the strains prevailed in the Far East. Cluster 2 comprised those of subsequently affected regions (Boryeong, Yongin, and Chungju), and was further diverged from the Cluster 1. The result of phylogenetic analysis indicated that the Korean strains may have evolved from a common ancestor of the Pan Asia strains, and that at least 2 phylogenetically clustered variants within the same lineage were prevalent during the epidemic. The potential origin and sources of the virus introduction to Korea were discussed.     

West Nile virus infection of Thoroughbred horses in South Africa (2000-2001)

REASONS FOR PERFORMING STUDY: West Nile virus (WNV) infection is endemic in southern Africa. With the recent emergence of WNV infection of horses in Europe and the USA the present study was performed to estimate the risk of seroconversion to WNV in a cohort of 488 young Thoroughbred (TB) horses. OBJECTIVES: To estimate the risk of seroconversion to WNV among a cohort of South African TB yearlings sold at the 2001 National Yearling Sales (NYS) and to determine whether the risk varied geographically. Two horses were also infected with a recent South African isolate of WNV to evaluate its virulence in horses. METHODS: Serum samples were collected from the cohort of 488 TB yearlings at the 2001 NYS. Serum samples that were collected from the same horses at the time that they were identified were sourced from our serum bank. Sera from 243 of the dams that were collected at the time that the foals were identified were also sourced from our serum bank. These sera were subjected to serum neutralisation (SN) tests for antibody to WNV. RESULTS: Approximately 11% of yearlings seroconverted to WNV on paired serum samples collected from each animal approximately 12 months apart. Studfarms with WNV-seropositive yearlings were widely distributed throughout South Africa and SN tests on sera from their dams indicated that exposure to WNV was even more prevalent (75%) in this population. Neurological disease was not described in any of the horses included in this study and 2 horses inoculated with a recent lineage 2 South African isolate of WNV showed no clinical signs of disease after infection and virus was not detected in their blood. CONCLUSIONS: Infection of horses with WNV is common in South Africa, but infection is not associated with neurological disease. POTENTIAL RELEVANCE: In contrast to recent reports from Europe, North Africa, Asia and North America, the results of our field and experimental studies indicated that exposure of horses to the endemic southern African strains of WNV was not associated with neurological disease.