Scientists at Wageningen College have analyzed why there are discrepancies in Salmonella outcomes between the poultry farmers’ exams and people of the authorities.
The specialists analyzed the elements related to the distinction between constructive exams from routine preliminary Salmonella monitoring by poultry farmers and detrimental outcomes from a brand new check from the Netherlands Meals and Shopper Product Security Authority (NVWA). The brand new exams are primarily based on suspicions of a false constructive consequence from routine monitoring.
The work, commissioned by the Ministry of Agriculture, Nature and Meals High quality (LNV), gave an concept of the outcomes through the surveillance of Salmonella in Dutch grownup breeding flocks.
The researchers mentioned there may be good cause to make retesting the preliminary constructive outcomes of routine Salmonella monitoring doable within the EU once more. This might solely contain 10-15 instances per 12 months within the Netherlands. The nation needed to change its strategy in early 2020 as a consequence of stress from the European Fee to repeat the exams provided that there are “affordable doubts” a couple of first consequence.
Components Affecting Outcomes
The workforce acquired information on all Salmonella monitoring samples from the Dutch poultry affiliation AVINED from 2015 to 2019 and the outcomes of the brand new NVWA exams, which collected new samples on the farm utilizing the identical methodology because the poultry farmers, who have been swabs. of shoes.
NVWA took samples a median of at some point after receiving a constructive report of the routine monitoring check consequence and a median of 4 to 6 days after the routine monitoring sampling by the farmer.
The Netherlands had 300 to 400 grownup breeding flocks between 2015 and 2019. In complete, the NVWA retested 44 routine follow-up constructive samples from 25 completely different farms and 21 have been detrimental and regarded false positives. Subsequent routine follow-up samples have been largely detrimental, indicating the absence of Salmonella within the flocks.
Within the examine interval, there have been 18 completely different laboratories that examined for Salmonella for the poultry sector and 9 laboratories reported preliminary constructive samples. The labs the place greater than two false constructive samples have been detected, after NVWA affirmation, have been the websites that carried out probably the most testing. Roughly 70 p.c of all surveillance samples have been analyzed by them.
The constructive results of routine Salmonella monitoring may very well be incorrect as a consequence of contamination throughout sampling by the poultry farmer as a consequence of inadequate hygiene measures; throughout transport of boot swab samples, contamination of samples within the laboratory, false constructive outcomes as a result of traits and efficiency of the check, contamination of poultry homes with out an infection of chickens and vaccination. Contamination throughout sampling was the more than likely state of affairs adopted throughout transport and of the samples within the laboratory.
A detrimental retest within the affirmation check by NVWA may very well be incorrect as a result of company’s lack of sensitivity of sampling; the lab check just isn’t delicate sufficient or just a few micro organism are current; Salmonella inactivation throughout transport to the laboratory, intermittent Salmonella excretion; remedy of poultry with antibiotics; and acidification of consuming water after preliminary constructive sampling. Insensitivity of sampling and inactivation of Salmonella throughout transport have been the more than likely, however have been nonetheless categorised as very low in a chance evaluation.
Causes to retest preliminary positives
Estimates confirmed that about one of many two farms that originally examined constructive is definitely contaminated. Confirmatory prognosis would enhance the specificity of the system and the arrogance constructive prognosis signifies a real an infection, in accordance with the examine.
Solely a small fraction of routine Salmonella management samples are constructive on preliminary sampling. In earlier years, the NVWA retested the check and 48 p.c have been detrimental.
It’s unethical or detrimental to welfare to euthanize grownup poultry flocks primarily based on a constructive routine monitoring check consequence as a result of in solely about 50 p.c of instances this displays the true Salmonella standing of a flock, they mentioned. The specialists.
The poultry business protocol to farmers on carry out routine boot swab sampling signifies that the method may very well be liable to introducing contamination from outdoors the home.
The outcomes of proficiency exams carried out by the Nationwide Reference Laboratory for Salmonella present that accredited laboratories generally report false positives. It was really useful that audits involving Salmonella diagnostic exams carried out by laboratories be included within the regulation.
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