Attempted Control of Paratuberculosis in Dairy Calves by Only Changing the Quality of Milk Fed to Calves.

Pamela Steuer,Manuel Moroni,Carlos Tejeda,Michael Thomas Collins,Miguel Salgado,Cristobal Verdugo

doi:10.3390/ani11092569

Abstract

Simple SummaryMilk is an important transmission route of Mycobacterium avium subsp. paratuberculosis (MAP) for dairy calves. The aim of the present study was to assess the efficacy of milk treatments to prevent MAP infection transmission to calves. A one-year field longitudinal study was carried out. Newborn calves were assigned to one of four experimental groups. MAP numbers were estimated for treated and untreated milk. Infection progression was monitored monthly. After one year, calves were euthanized, and tissue samples examined grossly and by histopathology. Milk treatments were highly effective though MAP shedding was also observed in all groups. It was not enough to try to block MAP infection transmission controlling only the quality of milk consumed by calves.One of the important routes of Mycobacterium avium subsp. paratuberculosis (MAP) transmission in dairy calves is milk. The aim of the present study was to assess the efficacy of milk treatments to prevent MAP infection transmission to calves. A one-year longitudinal study was carried out. Newborn calves were assigned to one of four experimental groups: 5 calves received naturally MAP-contaminated milk, 5 calves received copper treated milk, 4 calves were fed calf milk replacer, and 3 were fed UHT pasteurized milk. MAP load in milk was estimated. Infection progression was monitored monthly. After one year, calves were euthanized, and tissue samples were cultured and visually examined. MAP was undetectable in milk replacer and UHT milk. Copper ion treatment significantly reduced the number of viable MAP in naturally contaminated milk. Fecal shedding of MAP was observed in all study groups but began earlier in calves fed naturally contaminated milk. Paratuberculosis control programs must place multiple hurdles between the infection source, MAP-infected adult cows, and the most susceptible animals on the farm, young calves. As our study shows, strict dependence on a single intervention to block infection transmission, no matter how important, fails to control this insidious infection on dairy farms.

Highlights

The pathobiology of Mycobacterium avium subsp. paratuberculosis (MAP) infections is complex
A year-long pilot longitudinal field study was carried out to assess the efficacy of milk treatments to prevent MAP infection transmission to dairy calves through naturally contaminated milk
Group A calves (n = 5) received milk naturally contaminated with MAP, and group B calves (n = 5) were fed the same MAP-infected milk after first being treated with a novel decontamination tool based on copper ions

Summary

Introduction

The pathobiology of Mycobacterium avium subsp. paratuberculosis (MAP) infections is complex. Mainly ruminants, become infected at an early age, neonates being the most susceptible [1,2]. This obligate intracellular pathogen invades and replicates within macrophages [3]. MAP evades the host immune system leading to a chronic progressive infection with a long incubation period [1,3]. The available diagnostic tests have high rates of false-negative results (low diagnostic sensitivity), making identification of MAP-infected adult cattle, and infection control, on farms challenging and hampering national control programs [7]

Objectives

Methods

Results

Discussion

Conclusion