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.

A phylogenetic study of South African Newcastle disease virus strains isolated between 1990 and 2002 suggests epidemiological origins in the Far East.

Crocodiles and ostriches are very sensitive to stress, and the ideal conditions for intensive rearing have not yet been established. Consequently, mortality is often directly linked to conditions on the farm. Crocodile and caiman pox, adenoviral hepatitis, mycoplasmosis, chlamydiosis and coccidiosis are crocodile-specific infections with reservoirs in wild populations and adult wild-caught breeding stock. Other important conditions are salmonellosis, non-specific septicaemia, trichinellosis, the nutritional diseases osteomalacia, fat necrosis and gout, as well as winter sores. The only ostrich-specific transmissible disease is libyostrongylosis. Other important conditions are Newcastle disease, avian influenza, fading chick syndrome, tibiotarsal rotation and enteritis. No cases of coccidiosis in ostriches have ever been confirmed.

Diseases of farmed crocodiles and ostriches.

Ostrich meat may be consumed as a healthy alternative to beef. The establishment of ostrich farming systems is not sufficient to satisfy consumer demand without the use of a successful production and marketing strategy. Given the current export driven nature of the industry in Southern Africa and the need for the development of a domestic market, a good understanding of the position of ostrich meat in the marketing mix and the key elements in meat processing is necessary.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/B0628E7568CCF1B7F5AFB5E2D4DF6881/S0043933999000355a.pdf/div-class-title-ostrich-meat-an-important-product-of-the-ostrich-industry-a-southern-african-perspective-div.pdf

Ostrich meat, an important product of the ostrich industry: a southern African perspective

Newcastle disease (ND) in ostriches was first reported in zoo birds in the 1950s. An outbreak of ND in commercial ostriches in Israel was reported in 1989, but of more significance were the ND infections of ostriches in southern Africa during the 1990s as a result of assumed spread from commercial domestic fowl. The latter outbreaks were of particular concern due to the boom in international trade in ostriches and their products at that time. ND virus appeared to spread only slowly through affected ostrich flocks, and the clinical signs and mortality seen varied considerably with age. In field and experimental infections, morbidity, mainly in the form of nervous signs, and mortality could be extremely high in young birds but low or absent in adults. Characterization of ND viruses isolated during outbreaks in ostriches has shown them to be indistinguishable from viruses infecting chickens in the locality. Experimental challenge has shown ND poultry vaccines to be protective in ostriches, and several workers have proposed vaccine regimens employing both live and inactivated vaccines, usually given more frequently and employing much higher doses than recommended for chickens. Indirect and blocking enzyme-linked immunosorbent assay (ELISA) tests have been developed for the detection of ND antibodies in ostrich sera. Although some reports have suggested problems using the haemagglutination inhibition(HI)tests, others have recorded good correlation between ELISA, HI and virus neutralization tests. Because of their size and, as a consequence, the method of rearing, ostriches are quite different to conventional poultry and respond differently, in terms of disease and spread, when infected with ND virus. However, at present, for the international control of ND, there would appear to be little alternative to treating ostriches as poultry for the purposes of trade.

Newcastle disease in ostriches (Struthio camelus) - a review.

Ostrich production is highly management intensive. The ability to sustain long term profitability is dependent upon the use of strict management techniques by the producer and his workforce. Import...

https://www.tandfonline.com/doi/pdf/10.1079/WPS20000019

Critical factors in ostrich ( Struthio camelus australis ) production: a focus on southern Africa

VERWOERD, D.J ., GERDES, G.H ., OLIVIER, A & WILLIAMS, R. 1997. Experimental infection of vaccinated slaughter ostriches with virulent Newcastle disease virus. Onderstepoort Journal of Vet­ erinary Research, 64:213-216 A virulent Newcastle disease virus (NOV) isolate from an outbreak in commercial poultry, with viru ­ lence indices of MDT= 47-48 h; IV PI= 2,17 and ICPI = 1 ,8 ; was used to inoculate 1 Ox vaccinated (standard poultry vaccines) as well as 1 Ox unvaccinated slaughter ostriches via intratracheal, ocu ­ lar and nasal routes, in a controlled environment. All unvaccinated ostriches developed clinical signs (mainly respiratory); two of them died while the other eight recovered. No vaccinated ostriches de­ veloped any clinical signs. All remaining (18) ostriches were slaughtered 14 d after the last mortal­ ity. Virulent NOV could be re-isolated from the dead birds , but not from organs, muscle (fresh) , mus­ cle (24 h chilled) , gastro-instestinal tract, bone-marrow or respiratory system taken from the slaughtered ostriches. It is suggested that it would be extremely unlikely that the international trade in ostrich meat could act as a mechanism for spreading virulent NOV from endemic to non-endemic parts of the world .

/pdf/experimental-infection-of-vaccinated-slaughter-ostriches-3gwbtorvwv.pdf

Experimental infection of vaccinated slaughter ostriches with virulent Newcastle disease virus

The presence of virulent Newcastle disease virus (NDV) since the 1993-94 epidemic in southern Africa holds major implications for the export of ostrich products from this region. A challenge experiment with this field strain was conducted in open-air feedlot facilities under strict biosecurity measures. The experiment was designed to follow vaccination and preslaughter quarantine regulations currently enforced in South African export ostrich facilities in order to determine the viremia period and immune response under these specific circumstances. One hundred forty-three slaughter ostriches were allocated into three test groups, according to the time period between pretrial vaccination and challenge (1-2 mo, 2-4 mo, 4-6 mo), and an unchallenged control group. All birds in the test groups were challenged by oral, tracheal, and ocular routes with a field isolate of NDV. They were slaughtered over the next 4 wk on nine separate occasions and bled on 12 occasions. Virus isolation was attempted from seven sets of pooled samples from each bird to determine the viremia period and the serum antibody concentrations were measured by hemagglutination inhibition (HI) and enzyme-linked immunosorbent assay (ELISA) methods to establish an immune response curve. NDV could be back-isolated only up to day 9 postinfection and from only six ostriches with poor immune response titers and corresponding to a rise in antibody levels above an indirect ELISA optical density reading of 0.33. Virus could be recovered only from brain and respiratory tract tissue. The HI test was less sensitive than the ELISA. Immune response curves did not differ significantly between the groups and peaked on day 14 post-infection. From these data, ELISA titers would appear to be a good indicator of the probability that an ostrich will be clinically infected after velogenic NDV challenge. These results also suggest that the current vaccination schedule enforced by the South African Veterinary Authorities results in protective immunity in up to 95% of slaughter ostriches from export approved facilities. The standard 30-day preslaughter quarantine period introduced as part of Crimean-Congo hemorrhagic fever virus control measures also appears sufficient to encompass the determined NDV viremia period of 9-11 days in slaughter ostriches.

https://www.jstor.org/stable/info/1592641

D.J. Verwoerd

Papers

Experimental infection of vaccinated slaughter ostriches with virulent Newcastle disease virus

Experimental infection of vaccinated slaughter ostriches in a natural, open-air feedlot facility with virulent Newcastle disease virus