Paratuberculosis (or Johne’s disease) is a chronic, intestinal disease of ruminants caused by infection with Mycobacterium avium subsp. paratuberculosis (MAP). The ailment results in production losses from reduced milk output in dairy herds and increased involuntary culling. A few weeks after infection, the humoral response of the host animal is turn on and circulating antibodies can be detected by serological methods. The enzyme- linked immunosorbent assay (ELISA) technique is known to be the best alternative in MAP detection in animal herd as it offers speed and economy. Ovine paratuberculosis has a worldwide distribution and control measures have been established in some countries for eradication purposes. In Italy, few investigations have been done in relation to MAP infection in ovine farms and the prevalence in the Marche region is unknown. In order to investigate the MAP seroprevalence in ovine dairy farms, a survey on 2086 sheep randomly chosen from 38 farms in Ancona and Macerata provinces of Marche region (Dataset A) was carry out. Moreover, to evaluate the possibility of replacing serum with milk sample in the identification of MAP infected ovine flocks, a comparative study was carried out in central Italy on 17 dairy farms (Dataset B). Fresh milk and serum samples were collected from 702 randomly chosen sheep and tested by indirect ELISA (Pourquier®, Paratuberculosis ELISA kit, Montpellier, France). The sheep were of the Comisana, Massese, Sarda, Sopravissana, Fabrianese breeds above two years of age, at early/late or peak lactation period. In Dataset A, 28 herds (73.7%) resulted MAP infected with a seroprevalence of 6.29% (CI95 5.23-7.34; n=2086) of sampled sheep in both provinces. The seroprevalence was much higher in Macerata than in Ancona province (χ=5.75, P=0.0165). A higher number of MAP seropositive sheep were recorded in the large herds than in the small and medium herds’ consistence (χ=4.90, P=0.0269), and a greater percentage of seropositive sheep were obtained among sheep that were at early or late lactation stage during sampling (χ=5.12, P=0.0237). The evaluation of 1404 samples in Dataset B postulated a substantial agreement between serum and milk ELISA results, with a kappa value of 0.67, higher at early and late (k=0.78) than in peak (k=0.54) lactation, in agreement with the Immunoglobulin G (IgG) rising in the milk in the beginning and at the end of lactation. MAP infection was diagnosed in 54 (7.75%) and in 37 sheep (5.31%; χ2=3.4, P=0.0653) by serum and milk ELISA, respectively. Higher mean OD values were observed in serum (1.71 ± SD 0.59) than in milk positive samples (1.48 ± SD 0.77; t=-1.60, P=0.1128). The serum ELISA was able to identify more MAP positive sheep; nevertheless milk ELISA could be a good alternative, an available, cheaper and more feasible test to detect MAP infection in dairy sheep flocks by bulk tank milk. Furthermore, a fair (k=0.43) and slight (k=0.33) agreements were observed between milk ELISA – Ziehl Nelseen staining and milk ELISA – bacterial culture. The overall result suggests that ovine paratuberculosis have a remarkable clustered distribution in Ancona and Macerata provinces of Marche region in Central Italy, and that consumption of milk and cheese manufactured from raw ovine milk might lead to transmission of MAP to humans. Moreover, the normative (Intesa Stato Regioni of 25/1/2007), that defines the criterions of acceptability of raw milk sold directly to consumers, individualizes analytical parameters for the most important bacterial agents of food-borne illnesses but these do not include emergent pathogens like MAP. Thus a precautionary approach from public health authorities should be warranted and further investigations are needed to estimate the potential risk for consumers’ health.
Epidemiological studies of Ovine Paratuberculosis (Ovine Johne’s disease – OJD): study design and prevalence estimates in Marche region (central Italy)
NGU NGWA, VICTOR
2011-03-01
Abstract
Paratuberculosis (or Johne’s disease) is a chronic, intestinal disease of ruminants caused by infection with Mycobacterium avium subsp. paratuberculosis (MAP). The ailment results in production losses from reduced milk output in dairy herds and increased involuntary culling. A few weeks after infection, the humoral response of the host animal is turn on and circulating antibodies can be detected by serological methods. The enzyme- linked immunosorbent assay (ELISA) technique is known to be the best alternative in MAP detection in animal herd as it offers speed and economy. Ovine paratuberculosis has a worldwide distribution and control measures have been established in some countries for eradication purposes. In Italy, few investigations have been done in relation to MAP infection in ovine farms and the prevalence in the Marche region is unknown. In order to investigate the MAP seroprevalence in ovine dairy farms, a survey on 2086 sheep randomly chosen from 38 farms in Ancona and Macerata provinces of Marche region (Dataset A) was carry out. Moreover, to evaluate the possibility of replacing serum with milk sample in the identification of MAP infected ovine flocks, a comparative study was carried out in central Italy on 17 dairy farms (Dataset B). Fresh milk and serum samples were collected from 702 randomly chosen sheep and tested by indirect ELISA (Pourquier®, Paratuberculosis ELISA kit, Montpellier, France). The sheep were of the Comisana, Massese, Sarda, Sopravissana, Fabrianese breeds above two years of age, at early/late or peak lactation period. In Dataset A, 28 herds (73.7%) resulted MAP infected with a seroprevalence of 6.29% (CI95 5.23-7.34; n=2086) of sampled sheep in both provinces. The seroprevalence was much higher in Macerata than in Ancona province (χ=5.75, P=0.0165). A higher number of MAP seropositive sheep were recorded in the large herds than in the small and medium herds’ consistence (χ=4.90, P=0.0269), and a greater percentage of seropositive sheep were obtained among sheep that were at early or late lactation stage during sampling (χ=5.12, P=0.0237). The evaluation of 1404 samples in Dataset B postulated a substantial agreement between serum and milk ELISA results, with a kappa value of 0.67, higher at early and late (k=0.78) than in peak (k=0.54) lactation, in agreement with the Immunoglobulin G (IgG) rising in the milk in the beginning and at the end of lactation. MAP infection was diagnosed in 54 (7.75%) and in 37 sheep (5.31%; χ2=3.4, P=0.0653) by serum and milk ELISA, respectively. Higher mean OD values were observed in serum (1.71 ± SD 0.59) than in milk positive samples (1.48 ± SD 0.77; t=-1.60, P=0.1128). The serum ELISA was able to identify more MAP positive sheep; nevertheless milk ELISA could be a good alternative, an available, cheaper and more feasible test to detect MAP infection in dairy sheep flocks by bulk tank milk. Furthermore, a fair (k=0.43) and slight (k=0.33) agreements were observed between milk ELISA – Ziehl Nelseen staining and milk ELISA – bacterial culture. The overall result suggests that ovine paratuberculosis have a remarkable clustered distribution in Ancona and Macerata provinces of Marche region in Central Italy, and that consumption of milk and cheese manufactured from raw ovine milk might lead to transmission of MAP to humans. Moreover, the normative (Intesa Stato Regioni of 25/1/2007), that defines the criterions of acceptability of raw milk sold directly to consumers, individualizes analytical parameters for the most important bacterial agents of food-borne illnesses but these do not include emergent pathogens like MAP. Thus a precautionary approach from public health authorities should be warranted and further investigations are needed to estimate the potential risk for consumers’ health.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
