Mycobacterium aviumsubspeciesparatuberculosisseroconversion in dairy cattle and its association with raised somatic cell count

Abstract

This retrospective case–control study investigates the relationship between seroconversion to Mycobacterium avium subspecies paratuberculosis (MAP) and raised somatic cell count (SCC). The study consists of 112 case cows from three dairy farms in the UK; for each case cow with a positive antibody titre, there was a seronegative control cow for comparison. Seroconversion was monitored using milk ELISA antibody titres for MAP taken at quarterly intervals. SCCs were recorded at the time a positive antibody titre was first recorded as well as at the previous and subsequent milk recording in order to explore a temporal relationship between the two events. The previous and subsequent milk recordings were a month before and after seroconversion was identified. The results showed that cows that were infected with MAP had an increased SCC around the time that they first became seropositive, providing evidence for a temporal relationship between the two events; high SCCs were particularly prevalent before and at the time of first detecting seroconversion. The explanation is being discussed that potentially an underlying, currently not studied, factor may be predisposing both events, the progression of paratuberculosis is predisposing the host to mastitis, or indeed intramammary infections help initiate paratuberculosis progression.

A scoping review on associations between paratuberculosis and productivity in cattle

“…Significantly higher SCC in MAP positive animals or herds than in negative animals or herds were reported in several studies ( 33 , 42 , 62 , 66–68 ). Ozsvari et al ( 42 ), for example, found that milk ELISA positive cows had on average a higher SCC by 41.4 × 1,000 cells/ml, which is equivalent to an increase of 35.8%.…”

“…A significant decrease in milk yield for positive animals was observed in most studies, but a significant increase in milk yield, was also reported in few publications, depending on the stage of infection ( 30 , 31 , 50 , 61 ). In six publications, no significant difference was observed ( 33 , 46 , 47 , 62–64 ) and in five publications it was not stated whether the observed difference was significant ( 34 , 44 , 49 , 65 , 66 ).…”

“…The association between MAP infection and the amount of produced milk fat and protein were investigated in 16 publications ( Table 8 ). Studies, in which effects were not quantified, ( 61 , 62 ), where milk fat and protein were not looked at individually ( 65 ), where the positivity level was not dichotomous ( 54 ) and where the positivity level was defined on herd and not on individual animal level ( 64 ) are not listed in the table. Differences in milk protein of modeled data between PTB positive and negative animals at dichotomous level ( Table 8 ) ranged from −27.94 kg/lactation to 1.82 kg/lactation with a median of −14.41 kg/lactation per positive cow ( Table 9 ).…”