The ecology of M. paratuberculosis in biofilms (complex communities of microbes, and the slime secreted by these microbes, that cover surfaces of pipes and other surfaces exposed to bacteria-containing fluids) has not been studied until recently. This pathogen readily forms biofilms that may maintain their presence in water distribution systems, increase their resistance to chlorination and serve as hidden sources of contamination in the farm environment.
Livestock watering troughs were the focus of several recent studies. An inoculum of MAP (107/ml) was added to the water in four types of troughs (concrete, plastic, stainless steel and galvanized steel).
After 2 weeks, the organism could not be found suspended in the water, but in each case a biofilm had formed on the trough material with high concentrations of M. paratuberculosis. This in fact had occurred within three days of inoculation, and the organisms persisted for more than 300 days on concrete troughs.
Persistence of M. paratuberculosis was lowest on stainless steel, followed by plastic, galvanized steel and concrete. When 2ppm chlorine was added to the trough water less than 1% of bacteria remained on stainless and galvanized steel trough materials.
To reduce exposure of susceptible animals to M. paratuberculosis on infected farms, the authors recommended best management practices should include cleaning out and removing slime build-up on trough surfaces on a regular basis. In choosing new troughs, stainless steel is recommended.
Bolster, C.B., Cook, K.L., Haznedaroglu B., Walter, S. 2009. The Transport of Mycobacterium avium subsp. paratuberculosis through Saturated Aquifer Materials. Letters in Applied Microbiology. 48:307-312
Cook, K.L., Britt, J.S., Bolster, C.B. 2010a. Survival of Mycobacterium avium subsp. paratuberculosis in biofilms on livestock watering trough materials Vet. Micro. 141:103-109
Cook, K.L., Bolster, C.B., Britt, J.S., Rothrock, M. 2010b. Effect of watering trough chlorination on persistence of Mycobacterium avium subsp paratuberculosis. Bovine Practitioner. 44:69-76.
Like its closest cousin, M. avium, MAP can infect and replicate in free-living amoeba such as Acanthamoeba. These unicellular organisms common in aquatic environments act as free-living macrophages and potentially offer an ecological niche outside the host animal where MAP replication or at least persistence can occur. Moreover, the virulence of the organism may be enhanced by growth inside these amoebae. The adjacent image shows MAP inside Acanthamoeba castellanii (Whan et al. BMC Microbiology 6:63, 2006).
On the subject of environmental survival of MAP, the 1944 publication by Lovell et al. has become a classic reference. A series of studies using naturally infected bovine feces were conducted in which the infected fecal matter was exposed to a variety of natural conditions such as freezing, drying, sunlight, changes in ambient temperature, and rain, with regular attempts to reisolate MAP. In general they found survival of MAP in feces kept outdoors up to 152 to 246 days depending on specific conditions. Drying of soil appeared to shorten survival. The authors recommend considering a pasture contaminated by the organism as a potential source of infection for at least one year given the longevity of MAP. They mention that this supports recommendations of earlier workers (1929-1933). The commonly made statement that MAP survives a year on pastures, found in most literature on Johne's disease, likely originates from the work of Lovell et al.
MAP is resistant to heat, cold, drying and acidic conditions, but does not replicate in the environment. As an obligate pathogen, MAP in the environment does die off completely, but not quickly. When a premise is contaminated by MAP-containing manure, approximately 90% are believed to die off within a few months, but MAP in low numbers can be recovered for more than a year. The relevance of this persistence at low levels to new cases of infection is not known. In Australia, MAP could be isolated (albeit from fewer and fewer samples over time) from shaded soil (including soil shaded by crops) up to 55 weeks, and in shaded trough water at 48 weeks. Even greater longevity was noted in trough sediment. MAP was isolated from grasses germinating through manure-laden soil again in the pattern observed for MAP isolation from soil: greater MAP longevity was seen in grasses grown from completely versus 70% shaded soil boxes (24 versus 9 weeks). This study’s comparison of shaded versus partially shaded sites led the authors to conclude that diurnal temperature changes was more relevant in hastening complete MAP die-off than was just the UV radiation itself, and that removing vegetation to maximize temperature changes at soil level may be beneficial. Based on these data Whittington et al. in 2004, contaminated drinking water may remain a reservoir for new infections longer than contaminated ground. This publication also provides an excellent table of prior research on MAP survival in soil. Other work from that very productive research group published in 2009 demonstrated that MAP can adhere to soil particles and that this is heavily influenced by soil pH.
management is a component of domestic agriculture enterprises. Modes of dispersal
include spreading it on fields, injection into the soil and slurry pit storage
for later dispersal.
the first comprehensive study of its kind on survival of MAP in slurry in Denmark in 1977. In his work he used cattle slurry (pH 8.5, dry matter
7%), swine slurry (pH 8.3, dry matter 8.3%), and a mixture of the two (pH8.4,
dry matter 7.7%). After spiking each slurry preparation with 3 x 107 MAP/ml, he bubbled a mixture of hydrogen and nitrogen gas
through the slurry to secure anaerobic conditions and then stored the slurry at
5°C or 15°C. Jörgensen reported that the number of colonies of M.
paratuberculosis isolated on modified Löwenstein-Jensen medium dropped
drastically between sampling days 1 and day 7 but then remained relatively stable
until recovery of the organism stopped indicating the limit of survival. At 5°C
the survival time was 252 days in all three kinds of slurry, and at 15°C it
was 182 days in swine slurry, 98 days in cattle slurry, and 168 days in mixed
slurry. Comparable findings have been reported on survival of M. bovis
in cattle slurry.
Correctly managed composted organic material may be effective in killing MAP, but research on the topic is limited. This is consistent with time-temperature profiles of properly composted animal waste and thermal survivability characteristics of MAP.
Dhand, N. K., J. A. Toribio, and R. J. Whittington. 2009. Adsorption of Mycobacterium avium subsp. paratuberculosis organisms to soil particles. Appl. Environ. Microbiol. 75:5581-5585.
Doyle TM. Johne's disease, 1956. Vet Rec 68:869-878.
Falkinham III, J.O., C.D. Norton, and M.W. LeChevallier. 2001. Factors influencing numbers of Mycobacterium avium, Mycobacterium intracellulare, and other mycobacteria in drinking water distribution systems. Appl. Env. Microbiol. 67:1225-1231.
Grewal, S. K., S. Rajeev, S. Sreevatsan, and F. C. Michel, Jr. 2006. Persistence of Mycobacterium avium subsp. paratuberculosis and other zoonotic pathogens during simulated composting, manure packing, and liquid storage of dairy manure. Appl.Env.Microbiol. 72:565-574.
Johnson-Ifearulundu YJ, Kaneene JB. Relationship between soil type and Mycobacterium paratuberculosis, 1997. J Am. Vet. Med. Assoc. 210:1735-1740.
Olsen JE, Jörgensen JB, Nansen P. On the reduction of Mycobacterium paratuberculosis in bovine slurry subjected to batch mesophilic or thermophilic anaerobic digestion, 1985. Agricultural Wastes 13:273-280.
Pickup, R. W., Rhodes, G., Sidi-Boumedine, K., Bull, T. J., Weightman, A., Arnott, S., and Hermon-Taylor, J. 2005. Mycobacterium avium subspecies paratuberculosis in the catchment and water of the river Taff in South Wales, United Kingdom and its potential relationship to clustering of Crohn's disease in the city of Cardiff. Appl. Env. Microbiol. 71:2130-2139.
Whan, L., I. Grant, and M. Rowe . 2006. Interaction between Mycobacterium avium subsp. paratuberculosis and environmental protozoa. BMC Microbiology 6:63-69.
Whittington, R. J., D. J. Marshall, P. J. Nicholls, I. B. Marsh, and L. A. Reddacliff. 2004. Survival and dormancy of Mycobacterium avium subsp. paratuberculosis in the environment. Appl. Env. Microbiol. 70:2989-3004.
Whittington, R. J., I. B. Marsh, and L. A. Reddacliff. 2005. Survival of Mycobacterium avium subsp. paratuberculosis in dam water and sediment. Appl. Env. Microbiol. 71:5304-5308.