Publicação
Bovine mastitis due to coagulase-negative staphylococci and the role of minor pathogens on mastitis
| Resumo: | Bovine mastitis is the most common disease of dairy cows. To implement efficient control measures, it is generally necessary to diagnose the relevant aetiologic agents. Coagulasenegative staphylococci (CNS) and Corynebacterium spp. are considered minor mastitis pathogens because of the mild impact they have on udder health. Despite that, they are the most common agents isolated from milk samples in several large scale surveys worldwide. The objectives of this study were to evaluate if there were differences in pathogenicity between individual CNS species, to evaluate if alternative sampling or diagnostic techniques could more accurately determine in which cases the aforementioned minor pathogens were responsible for mastitis, and to determine if treatment of CNS infected quarters was a costeffective control measure. We followed 111 intramammary infections due to CNS for up to 48 weeks in four commercial dairy farms. Duration of infection had a mean of 188 days and was not significantly different between CNS species; geometric mean quarter somatic cell count (SCC) overall was 132,000 cells/ml and was also not significantly different between CNS species. There were differences in diversity between CNS species, with Staphylococcus epidermidis and Staphylococcus simulans showing less diversity than Staphylococcus haemolyticus, the epidemiological significance of which is debated. Freezing milk samples overnight at -20ºC did not increase detection of intramammary bacteria in milk samples. Use of a real-time PCR-based test allowed for detection of udder pathogens beyond the ones identified using conventional bacteriology in milk samples with a high SCC that were culture negative or that yielded CNS or Corynebacterium bovis shown by conventional bacteriology. Single quarter milk samples were collected in duplicate from 132 dairy cows in a commercial dairy farm, with the standard technique and by use of a cannula surpassing the teat canal. There was a significant difference between the two sampling techniques for recovery of Corynebacterium spp. and for culture-negative samples. The observed difference could not be attributed to a particular sampling order and no significant change was observed in quarter SCC between the sampling day and seven days later, indicating iatrogenic IMI following use of the alternative technique was not an issue. Use of a deterministic economic model allowed to determine that in most situations lactational treatment of subclinical mastitis due to CNS would result in a net financial loss, on average of €38.74 per treated quarter. Taken together, these results indicate that CNS have a low impact in terms of udder health, with little differences between individual species. Treating CNS subclinical mastitis during the lactation is not cost-efficient and should therefore not be advised. Using a RTPCR and sampling with a teat cannula might improve diagnosis of mastitis etiology. |
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| Autores principais: | Bexiga, José Ricardo Dias |
| Assunto: | minor mastitis pathogens diagnosis economics coagulase-negative staphylococci Corynebacterium spp. diversity PFGE impact udder health bovine agentes patogénicos menores de mastites diagnóstico estudo económico staphylococci coagulase-negativos diversidade impacto saúde do úbere bovino |
| Ano: | 2011 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Bovine mastitis is the most common disease of dairy cows. To implement efficient control measures, it is generally necessary to diagnose the relevant aetiologic agents. Coagulasenegative staphylococci (CNS) and Corynebacterium spp. are considered minor mastitis pathogens because of the mild impact they have on udder health. Despite that, they are the most common agents isolated from milk samples in several large scale surveys worldwide. The objectives of this study were to evaluate if there were differences in pathogenicity between individual CNS species, to evaluate if alternative sampling or diagnostic techniques could more accurately determine in which cases the aforementioned minor pathogens were responsible for mastitis, and to determine if treatment of CNS infected quarters was a costeffective control measure. We followed 111 intramammary infections due to CNS for up to 48 weeks in four commercial dairy farms. Duration of infection had a mean of 188 days and was not significantly different between CNS species; geometric mean quarter somatic cell count (SCC) overall was 132,000 cells/ml and was also not significantly different between CNS species. There were differences in diversity between CNS species, with Staphylococcus epidermidis and Staphylococcus simulans showing less diversity than Staphylococcus haemolyticus, the epidemiological significance of which is debated. Freezing milk samples overnight at -20ºC did not increase detection of intramammary bacteria in milk samples. Use of a real-time PCR-based test allowed for detection of udder pathogens beyond the ones identified using conventional bacteriology in milk samples with a high SCC that were culture negative or that yielded CNS or Corynebacterium bovis shown by conventional bacteriology. Single quarter milk samples were collected in duplicate from 132 dairy cows in a commercial dairy farm, with the standard technique and by use of a cannula surpassing the teat canal. There was a significant difference between the two sampling techniques for recovery of Corynebacterium spp. and for culture-negative samples. The observed difference could not be attributed to a particular sampling order and no significant change was observed in quarter SCC between the sampling day and seven days later, indicating iatrogenic IMI following use of the alternative technique was not an issue. Use of a deterministic economic model allowed to determine that in most situations lactational treatment of subclinical mastitis due to CNS would result in a net financial loss, on average of €38.74 per treated quarter. Taken together, these results indicate that CNS have a low impact in terms of udder health, with little differences between individual species. Treating CNS subclinical mastitis during the lactation is not cost-efficient and should therefore not be advised. Using a RTPCR and sampling with a teat cannula might improve diagnosis of mastitis etiology. |
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