Control of Mycobacterium avium subsp. paratuberculosis infection on a New Zealand pastoral dairy farm

Abstract

Background Johne’s disease is a major production limiting disease of dairy cows caused by infection with Mycobacterium avium subsp. paratuberculosis in calf-hood. The disease is chronic, progressive, contagious and widespread with no treatment and no cure. Economic losses arise from decreased productivity through reduced growth, milk yield, fertility and also capital losses due to premature culling or death. Control chiefly centers upon removing those animals which actively shed bacteria and protecting calves from infection. A prolonged pre-clinical shedding phase, lack of test sensitivity, organism persistence and abundance in the environment as well as management systems that expose susceptible calves to infection make control challenging, particularly in pastoral, seasonal dairy systems. Combining a novel testing strategy to remove infected cows along with limited measures to protect vulnerable calves at pasture, this study reports the successful reduction over a four-year period of seroprevalence of cows testing positive for MAP infection in a New Zealand pastoral dairy herd. Results For all age groups considered the apparent seroprevalence of cows testing positive decreased from 297 / 1,122 (26%) in 2013–2014, to 24 / 1,030 (2.3%) in 2016–2017. Over the same period, the apparent seroprevalence in primiparous cows decreased from 39 / 260 (15%) to 7 / 275 (2.5%) and in multiparous cows from 258 / 862 (29.9%) to 17 / 755 (2.3%). The reported proportion of calved cows culled annually from suspected clinical Johne’s disease fell from 55 / 1,201 (5%) in the year preceding the control program to 5 / 1,283 (0.4%) in the final year of the study. Conclusions On this farm , reduction in the prevalence of infection was achieved by reducing the infectious pressure through targeted culling of heavily shedding animals together with limited measures to protect calves at pasture from exposure to Mycobacterium avium subsp. paratuberculosis . Whilst greater protection of young animals through separation from infected cows and their colostrum and milk would have reduced the risk of neonatal infection, this study demonstrates, in this case, that these management measures while prudent were not essential for effective reduction in the prevalence of MAP infection.

Identification of Mycobacterium avium subsp. paratuberculosis (MAP) in Sheep Milk, a Zoonotic Problem

“…Interestingly, the bulk tank milk (BTM) test is one the most economical and efficient herd-level analyses for screening of JD, which provides a general overview of the health status of the animals in each herd, especially as the presence of asymptomatic animals can lead to underestimation of the sensitivity and specificity of the diagnostic assays [ 14 , 15 ]. Evidence of MAP was discovered in milk and feces cultured from both symptomatic and asymptomatic carriers [ 16 , 17 ].…”

Systematic Assessment of Mycobacterium avium Subspecies Paratuberculosis Infections from 1911–2019: A Growth Analysis of Association with Human Autoimmune Diseases

“…Aside from animal infections, MAP is responsible for soft-tissue and lymph-node infections in healthy humans and has been associated with Crohn’s disease and other autoimmune diseases in human as well [ 8 , 9 , 10 , 11 , 12 ]. The ease of faecal-oral dissemination of the pathogen through a number of ways such as feeding, milk/milk products, meat products, direct contact with infected animals, animal faeces/manure, water, and pasture [ 13 , 14 ] and abundance/persistent in the environment [ 15 , 16 , 17 ], constitute a greater public health risk and menace in general control of MAP; and thus, a greater threat in pre-urban, pastoral and rural communities. As these communities lack potable water supply and get their supplied from pastoral- activities impacted freshwater, which positioned them to contract MAP in a myriad of ways.…”

Mycobacterium Avium Paratuberculosis: A Disease Burden on the Dairy Industry

“…Studies show a prevalence of above 50% for MAP in dairy herds in countries operating intensive farming systems [ 40 ] with low levels (5%) of clinical disease [ 44 ]. Indeed, in the United States, prevalence ranges from 68 to 91% in dairy herds and 8% of beef herds [ 45 ] with estimates typically based on ELISA, fecal culture, or PCR techniques.…”

“…Diagnostic tools available for detection differ in their sensitivity and specificity, confounding data on herd prevalence. For example, the application of ELISA tests to detect MAP antibodies is confounded by common antigens between other Mycobacterium species such as M. tuberculosis and other MAC strains, reducing specificity [ 44 ]. The ELISA test detects specific MAP antibodies and is based on a humoral immune response in the animal, typically seen in late-stage clinical disease [ 48 ], rendering it ineffective for subclinical infections.…”

“…Differentiating between MAP and other mycobacterial infections should improve the ability of ELISA tests to determine prevalence rates. At present, prolonged preclinical shedding phase, lack of test sensitivity, MAP environmental persistence, and poor management systems allow MAP to persist particularly in pastoral, seasonal dairy systems [ 44 ].…”