RESEARCH ▶▶▶
Study reveals main risk factors for Newcastle disease in Brazil
A study done by the Brazilian Animal Health Defence Group (GDSA) has revealed several risk factors for the spread of Newcastle disease from backyard farms to commercial producers in São Paulo State, Brazil.
BY DANIEL AZEVEDO G
iven that it is a notifiable disease, Brazil has a pret- ty good indication of its NCD status. With the last official outbreak in 2006, researcher Luciano Laga- ta, director at the Animal Health Defence Group
(GDSA) of São Paulo State, led a new evaluation of the threat posed by Newcastle disease. In his view, backyard birds are disease reservoirs and have been an epidemiological issue for a long time. They are a permanent concern for poultry com- panies. “Poorly designed biomeasures or the total lack of them, along with continual contact with wild birds, make these backyard farms more susceptible to viral infections,” he says. Indeed, The World Organisation for Animal Health (for- merly OIE) recommends the use of risk analysis as a tool to prevent the spread of pathogens and to estimate the proba- bility of disease outbreaks. “It is carried out in four steps: risk identification, disease routes, outbreak management and communication with the relevant parties,” explains Lagatta.
Research The study sought to identify possible sources of infection and the transmission routes of the Newcastle disease virus in 104 backyard farms (2,423 animals) in the immediate vicinity of five large poultry farms in São Paulo State. Two of them were large companies focused on genetics and breeding. The researchers examined animal trachea swabs and manure samples. In addition, they asked backyard farm owners to fill in a questionnaire to be able to classify risk factors related to the introduction or spread of disease among these popula- tions. During the course of a year (October 2017 to October 2018), 81 backyard farms were visited (77.88% of the total) and 1,530 birds were tested. Of this total, 30 were ducks and were not included in the serological analysis. Five farmers would not allow the researchers onto their premises.
An NCD risk analysis comprises four steps: risk identification, disease routes, outbreak management and communication.
42 ▶ POULTRY WORLD | No. 8, 2021
Positive birds In total 533 samples were collected, representing 24% of registered birds. Altogether, 86 birds showed antibodies to the Newcastle virus, however, this did not mean that the disease was in circulation. “We did not see any signs of res- piratory or neurological prevalence, or a different mortality rate in the birds tested,” Lagatta emphasizes. Following the tests, the questionnaire identified six farms among these 46 backyard farms as those most likely to represent a risk. The principal conclusion was that the contact with wild birds in 39 of the farms posed the greatest risk. “In this case, the fac- tor to be worked on is preventing birds living in the wild from having contact with the farmed animals,” Lagatta explains. A second insight was that the biosecurity on the farms is ‘pre- carious’. Also noteworthy was the lack of veterinary care which would help with the preventive and curative aspects of infection. Another factor was that 74.4% of these producers have other growers as neighbours, in addition to the informal origin of their birds. Finally, there was the issue of the im- proper disposal of dead birds, often in household waste. The six farms pinpointed as the main risk hubs need more attention from their owners and, clearly, from the profes- sional poultry companies surrounding them. “The preven- tion of disease in backyard farms should be a shared re- sponsibility among poultry companies and, obviously, of the State veterinary service. We must invest in monitoring, communication and education campaigns to address these kinds of harmful health issues,” concludes Lagatta.
PHOTO: HANS PRINSEN
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