No abstract

Genetic comparisons were made of the fusion protein sequences of 155 Newcastle disease virus isolates collected in South Africa between 1990 and 2002. Their evolutionary relationships and origins are described. All of the lentogenic field isolates were shown to be derived from commercial vaccines. No true South African lentogenic wild type strain was identified. Furthermore, it was shown that almost all mesogenic isolates had avirulent F(0) cleavage site sequences. Three major epizootics occurred in South Africa during the period of this study. The first outbreak (1990/1991) was caused by viruses endemic to South Africa since the 1960's (genotype VIII) but were occasionally also isolated in 2000. Genotype VIIb viruses, implicated in the severe outbreaks during 1993/1994, persisted until 1999. Genotype VIId viruses, responsible for the most recent outbreak in 1999/2000, had their origins in the Far East like those of the two previous outbreaks.

The first recorded outbreak of avian influenza (AI) in South African chickens (low pathogenicity H6N2) occurred at Camperdown, KwaZulu/Natal Province (KZN) in June 2002. To determine the source of the outbreak, we defined the phylogenetic relationships between various H6N2 isolates, and the previously unpublished gene sequences of an H6N8 virus isolated in 1998 from ostriches in the Leeu Gamka region (A/Ostrich/South Africa/KK98/98). We demonstrated that two distinct genetic H6N2 lineages (sub-lineages I and II) circulated in the Camperdown area, which later spread to other regions. Sub-lineages I and II shared a recent common H6N2 ancestor, which arose from a reassortment event between two South African ostrich isolates A/Ostrich/South Africa/9508103/95 and (H9N2) /Ostrich/South Africa/KK98/98 (H6N8). Furthermore, the H6N2 sub-lineage I viruses had several molecular genetic markers including a 22-amino acid stalk deletion in the neuraminidase (NA) protein gene, a predicted increased Nglycosylation, and a D144 mutation of the HA protein gene, all of which are associated with the adaptation of AI viruses to chickens. The H6N2 NS1 and PB1 genes shared recent common ancestors with those of contemporary Asian HPAI H5N1 viruses. Our results suggest that ostriches are potential mixing vessels for avian influenza viruses (AIV) outbreak strains and support other reports that H6 viruses are capable of forming stable lineages in chickens.

A serological survey of leptospirosis in cattle originating from rural communities of the province of KwaZulu-Natal (KZN) in South Africa was carried out between March 2001 and December 2003. The survey was designed as a 2-stage survey, using the local dip tank as the primary sampling point. In total, 2021 animals from 379 dip tanks in 33 magisterial districts were sampled and tested with the microscopic agglutination test (MAT). The apparent prevalence at district level was adjusted for clustering and diagnostic test sensitivity and specificity and displayed in maps. The prevalence of leptospirosis in cattle originating from communal grazing areas of KZN was found to be 19.4% with a 95% confidence interval of 14.8-24.1 %. At district level the prevalence of leptospirosis varied from 0 to 63 % of cattle. Bovine leptospirosis was found to occur in communal grazing areas throughout the province with the exception of 2 districts. The southeastern regions showed a higher prevalence than other areas of the province; while in some of the northern and western districts a lower prevalence was noted. Several serovars were detected by the MAT and although Leptospira interrogans serovar pomona occurred most frequently, serovars tarrasovi, bratislava, hardjo, canicola and icterohaemorrhagica were also frequently identified. The findings of the survey are discussed

It is widely accepted that Newcastle disease is endemic in most African countries, but little attention has been afforded to establishing the sources and frequency of the introductions of exotic strains. Newcastle disease outbreaks have a high cost in Africa, particularly on rural livelihoods. Genotype VIIh emerged in South-East Asia and has since caused serious outbreaks in poultry in Malaysia, Indonesia, southern China, Vietnam and Cambodia. Genotype VIIh reached the African continent in 2011, with the first outbreaks reported in Mozambique. Here, we used a combination of phylogenetic evidence, molecular dating and epidemiological reports to trace the origins and spread of subgenotype VIIh Newcastle disease in southern Africa. We determined that the infection spread northwards through Mozambique, and then into the poultry of the north-eastern provinces of Zimbabwe. From Mozambique, it also reached neighbouring Malawi and Zambia. In Zimbabwe, the disease spread southward towards South Africa and Botswana, causing outbreaks in backyard chickens in early-to-mid 2013. In August 2013, the disease entered South Africa's large commercial industry, and the entire country was infected within a year, likely through fomites and the movements of cull chickens. Illegal poultry trading or infected waste from ships and not wild migratory birds was the likely source of the introduction to Mozambique in 2011.

A serological survey of Brucella abortus in cattle originating from communal grazing areas of Kwa Zulu Natal was carried out between March 2001 and December 2003. The survey was designed as a 2-stage survey, considering the diptank as the primary sampling unit. In total 46 025 animals from 446 diptanks of 33 magisterial districts were sampled and tested using the Rose Bengal test and Complement Fixation Test. The apparent prevalence at district level was adjusted for clustering, diagnostic test sensitivity and specificity, and mapped using ArcView version 3.3. The prevalence of brucellosis in communal grazing areas of Kwa-Zulu Natal was found to be 1.45 % (0.84-2.21 %) and varied from 0 to 15.6% between magisterial districts. In 19 of the 33 magisterial districts no serological reactors were observed. A large variation in prevalence was found within diptank areas. Brucellosis was found to be most prevalent in the northeastern area of the province. The findings of the survey are discussed

In South Africa from early 1989 onward, strains of Haemophilus paragallinarum not requiring nicotinamide adenine dinucleotide (NAD) have been isolated from commercial chickens suffering from infectious coryza. Fifteen of these field isolates were characterized by biochemical typing, serotyping, restriction endonuclease analysis (REA), and ribotyping. The chosen isolates represented diversity in geographic location, time of disease outbreak, and type of flock. All were typical of the species in biochemical properties, except that they were NAD-independent, and all were Page serovar A. REA was performed with three enzymes: HindIII, HpaII, and SspI. All isolates gave identical REA profiles with all three enzymes. Ribotyping was performed using a probe that consisted of the plasmid pUC19 into which the 16S rRNA operon of H. paragallinarum had been inserted. All 15 isolates gave the same ribotyping profile using each of the three enzymes. As a group, the NAD-independent strains gave REA profiles and ribotypes that were very different from a range of classic South African strains isolated before 1989. Our results strongly suggest that the NAD-independent isolates are clonal in nature.

A questionnaire survey of 315 cattle owners from the rural districts of KwaZulu-Natal was carried out. The aim of the survey was to improve our understanding of local farmers' perceptions and practices of animal disease prevention and control and to establish the extent of their relationship with veterinary services. The survey showed that many owners practice preventive measures such as deworming, tick control and vaccination. Traditional medicines were in use by over half the respondents (58.9 %). Diseases are regarded as an important management problem (56.1 %); ticks, worms and diarrhoea dominated the mentioned health problems in cattle. Veterinary services still play an important role and are a frequent source of advice to owners. The findings of the survey and their context are discussed