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.

Because of the fact that South Africa is a Newcastle disease virus (NDV)-endemic country, major concerns exist that the export of ostrich meat could transmit velogenic strains of this disease. The ability to transmit the virus could be reduced by effective vaccination of South African ostriches. In this study, two vaccination trials were conducted to assess serum antibody production in response to vaccination with La Sota strain NDV vaccines. To this end, a commercially available chicken anti-NDV enzyme-linked immunosorbent assay (ELISA) was modified for the detection of anti-NDV antibodies in ostrich serum. The results obtained with this ELISA were verified by comparison with an indirect ELISA. In the first trial, ostriches were immunized subcutaneously four times with different volumes of an inactivated vaccine and their immune response was determined from 2.5 mo up to the ideal slaughter age of 14 mo. Results indicated that ostriches responded in a dose-dependent manner and gave support for the vaccination schedule currently recommended to South African farmers. In a second trial, immunization by eyedrop with a live La Sota vaccine of 5-wk-old ostriches did not elicit a humoral immune response. The results indicate that it is highly unlikely that ostriches that have been vaccinated according to the recommended vaccination schedule can transmit the virus.

Antibody Responses to La Sota Strain Vaccines of Newcastle Disease Virus in Ostriches (Struthio camelus) as Detected by Enzyme-Linked Immunosorbent Assay

Knowledge regarding the role that immune mechanisms play in the protection of ostrich chicks against Newcastle disease virus (NOV) will be valuable in establishing effective vaccination regimes and thus in the control of NOV in ostriches. In chickens, effective control of NOV in chicks can be achieved by both passive (maternal) and active immunization. In this study, ostrich hen serum immunoglobulin G (lgG) and yolk IgY were isolated and characterized, and the transfer of maternal anti-NOV antibodies to the egg yolk determined using an enzyme-linked immunosorbent assay (ELISA). To this end, serum samples were collected from vaccinated and nonvaccinated ostrich hens and tested for anti-NOV antibodies. At the same time one egg was collected from each of these ostrich hens and the yolk tested for anti-NOV antibodies. Results indicated that anti-NOV antibodies were successfully transferred from the ostrich hen to the egg yolk. Local application of a live or inactivated NOV vaccine in ostriches has been postulated to stimulate the production of mucosal antibody and thus IgA. In this study, ostrich IgA was isolated, characterized and secondary rabbit anti-ostrich IgA antibodies produced for use in an anti-NOV ELISA. Trachea swabs were collected on a weekly basis after vaccination with a live La Sota vaccine, and tested for the presence of anti-NOV IgA antibodies. Results indicated that mucosal application of live La Sota vaccine stimulates mucosal IgA production against NOV. Stellenbosch University http://scholar.sun.ac.za

Immunological and epidemiological investigations in South African ostriches and penguins

The Codes of Practice developed for ratites in a number of countries place considerable importance on ensuring that the health of birds is closely monitored and that appropriate vaccines are used to prevent disease. Likewise, if the health of ratites is compromised, there are clear guidelines on actions required by farmers to improve the health of birds. The action required by persons in caring for the health of birds is a significant welfare responsibility. The welfare of ratites when using health as an indicator can range from minor ailments or infections with minimal concerns to the major health issues that cause considerable pain and discomfort to animals. When the death of the animal is potentially involved, immediate action is necessary to prevent mortality. Effective implementation of preventative health programmes that involve record keeping, preventative health measures, quarantine principles, biosecurity practices and monitoring of management practices can improve the efficiency of ratite farms and also improve bird health and welfare.

Ratite Health: Welfare Implications

This study was conducted to record, analyze and discuss the day-to-day practical aspects and constraints affecting the commercial production of ostriches (Struthio camelus) and emus (Dromaius novaehollandiae) in two ratite farms, A and B, in Al-Qassim area, Central Region of Saudi Arabia. In Farm A, where the original ostrich breeders were imported from France the new breeders (breeders produced in the Farm) started egg laying at the age of 19 months while the new emu breeders in the same Farm started egg laying at 22 months old. Ostriches in the two farms laid most of their eggs (73.5% and 64.9%) during day time (before sunset) while emus laid most of their eggs (98.1%) during night. Both original breeders of ostriches and emus were found to be more persistent in egg laying (85.9% and 72.6%) than their descendant breeders. About 11% of the ostrich eggs laid in Farm A throughout three seasons were found to be defective whereas 6.7% of the eggs laid in Farm B were defective. In emus, however, the average of the defective eggs throughout four production seasons was found to be 8.9%. The fertility of ostrich eggs in Farm A was found to be improving successively from season to another (32.4%, 55.6%, 60.7% and 61.2%) as well as with the progress of the single season before it drops at the end of the season (36.5%, 45.2%, 65%, 67% and 47%). Heat stress was found to reduce the fertility rate of ostriches. Emus were found to have higher overall mean fertility rates (70.3%) than ostriches in both Farms (52.5% and 58.4%). The overall mean hatchability rate of ostrich eggs (72.8%) was found to be higher than the overall mean fertility rate of ostrich eggs (52.5%) in four seasons. However, the overall mean hatchability rate of emu eggs (62.9%) was found to be lower than the overall mean fertility rate of emu eggs (70.3%) in three seasons. Developing ostrich and emu embryos had higher late embryonic mortality (60% and 66.4%) compared to early embryonic mortality (40% and 33.6% respectively). Emu chicks had higher (19.4%) incidence of congenital deformities than ostrich chicks (4.1%). The total weekly body weight gain of ostrich chicks in Farm B at the end of the first 14 weeks of life was higher (18350 g) compared to that in Farm A ostrich chicks (2600 g). The mean weekly body weight gain per ostrich chick that was hatched during summer was found to be higher (657.5 g; p<0.05) than the mean weekly body weight gain in chicks that were hatched during winter (356.75 g). The mortality rate of ostrich chicks during rearing phase (first 3 months of life) was 29% with non-consistent pattern throughout the season. The overall emu chick mortality rate during rearing phase (21.6%) was lower than that in ostrich chicks (29%), similarly, without specific pattern or behaviour. The main causes of mortality in ostrich chicks in Farm A were leg deformities, fading chick syndrome (F C S), Newcastle disease (N C D) and enteritis whereas the main causes of mortality in Farm A ostrich growers were sand impaction, Newcastle disease, leg deformities and enteritis. In Farm A ostrich breeders, the main causes of mortality were septicaemic pasteurellosis, wound infections, accidents, particularly those terminated into broken necks, and peritonitis. Causes of mortality in Farm B ostrich chicks included fading chick syndrome, leg deformities, enteritis and sand impaction. In Farm B growers, the main causes of mortality were leg deformities and septicaemic pasteurellosis whereas for Farm B breeders septicaemic pasteurellosis, accidents and fractures comprised the main causes of lethality. Leg deformities were the most common cause of mortality in Farm A emu chicks throughout the four seasons of study. There were no mortalities attributed to sand impaction or Newcastle disease in the emu chicks although these chicks were sharing the same premises with the ostrich chicks that suffered a severe NCD outbreak in Farm A in the year 2000. In emu growers, the main causes of mortality were leg deformities, suffocation and infected fighting wounds. Escherichia coli was isolated from 35.5% of the samples cultured from dead ostrich chicks in Farm A whereas Salmonella sp. organisms were isolated from 12.9% of the cultured samples. However, 22.6% of the cultured samples did not reveal any bacterial growth. For the emus, Escherichia coli was isolated from 33.3% while Salmonella species were isolated from 16.7% of the specimens (liver, yolk fluid and intestinal content) cultured from dead emu chicks. Among the different forms of leg deformities terminating lethally, tibiotarsal rotation (84%) comprised the most common one in ostrich chicks followed by splayed legs (11.9%). In ostrich growers in Farm A, again tibiotarsal rotation was found to be the most common killing form of leg deformities (78.5%) followed by slipped tendon (14%). In emu chicks, tibiotarsal rotation (98.8%) was the most common killing form of leg deformities followed by splayed legs (1.2%) whereas in emu growers, tibiotarsal rotation (99.4%) was the most common killing form of leg deformity followed by valgus rotation (0.6%).

Madeiros C

Papers

Vaccination of ostriches against Newcastle disease.