Molecular characterization of Mycobacterium avium subsp. paratuberculosis using multi-locus short sequence repeat (MLSSR) and mycobacterial interspersed repetitive units-variable number tandem repeat (MIRU-VNTR) typing methods

The aim of this study was to characterize 38 bovine strains of Mycobacterium avium subsp. paratuberculosis isolated in Ireland using 11 multi locus short sequence repeat (MLSSR) loci and 8 mycobacterial interspersed repetitive units-variable number of tandem repeat (MIRU-VNTR) loci. The discriminatory power of these two typing methods alone and combined was evaluated, as was the epidemiology of the isolates and the genotypes obtained. Using the MIRU-VNTR typing method (8 loci analysed), only 3 subtypes were detected with a discrimination index (DI) of 0.54, but one MIRU-VNTR type has not been identified in other studies. In contrast the MLSSR method (using 11 loci) differentiated the 38 MAP isolates into 18 types with DI of 0.92. Among these 18 types 6 have not been recorded previously. The combination of the 2 methods (MIRU-VNTR and MLSSR) produced 22 distinct genotypes giving a maximal DI of 0.94. According to the allelic diversity, some markers are more polymorphic than others and must be applied in priority for the differentiation of MAP bovine isolates. This is the first report of genotyping data for MAP on the island of Ireland and will be very useful for analysing its epidemiology, transmission and virulence.     

Genotypes of Mycobacterium avium subsp. paratuberculosis from South American countries determined by two methods based on genomic repetitive sequences

Mycobacterium avium subsp. paratuberculosis (MAP) is the causal agent of Johne's disease or paratuberculosis of ruminants and has been associated with Crohn's disease in humans. In this study, the genotypes of MAP obtained so far in South American countries using a combination of the subtyping methods Mycobacterial Interspersed Repeats Units-Variable Number of Tandem Repeats (MIRU-VNTR) and Multilocus Short Sequence Repeats (MLSSR) were analyzed. Through this analysis, seven different MIRU-VNTR genotypes and seven MLSSR genotypes have been detected. If both methods were combined, nine different genotypes were found. Results revealed the predominance of MIRU-VNTR genotype 1 (INMV 1) and MLSSR genotype A (7 g-10 g-4ggt) among MAP isolates from different host species in South America. These predominant MAP genotypes are also commonly detected in Europe and the United States. This predominance could be the result of higher animal infection ability or better culturability on solid media used for isolation. Further studies on molecular epidemiology of MAP must be carried out in South America to increase our knowledge of the global distribution of MAP.     

Different Mycobacterium avium subsp. paratuberculosis MIRU-VNTR patterns coexist within cattle herds

A better understanding of the biodiversity of Mycobacterium avium subsp. paratuberculosis (MAP) offers more insight in the epidemiology of paratuberculosis and therefore may contribute to the control of the disease. The aim of this study was to investigate the genetic diversity in bovine MAP isolates using PCR-based methods detecting genetic elements called Variable-Number Tandem Repeats (VNTRs) and Mycobacterial Interspersed Repetitive Units (MIRUs) to determine if multiple MAP strains can coexist on farms with endemic MAP infection. For 52 temporal isolates originating from infected cattle from 32 commercial dairy herds with known trading history, MIRU-VNTR analysis was applied at 10 loci of which six showed variation. Within the group of 52 isolates, 17 different MIRU-VNTR patterns were detected. One MIRU-VNTR pattern was found in 29 isolates, one pattern in four isolates, one pattern in three isolates, two times one MIRU-VNTR pattern was found occurring in two isolates, and 12 patterns were found only once. Eleven herds provided multiple isolates. In five herds a single MIRU-VNTR pattern was detected among multiple isolates whereas in six herds more than one pattern was found. This study confirms that between dairy farms as well as within dairy farms, infected animals shed MAP with different MIRU-VNTR patterns. Analysis of trading history and age within herds indicated that cows born within the same birth cohort can be infected with MAP strains exhibiting variations in the number of MIRU-VNTR repeats. These data indicate that such multiple genotypes of MAP can coexist within one herd.     

Variable number tandem repeat analysis of Mycobacterium bovis isolates from Gyeonggi-do, Korea

Bovine tuberculosis (TB) is a major zoonosis that''s caused by Mycobacterium bovis (M. bovis). Being able to detect M. bovis is important to control bovine TB. We applied a molecular technique, the variable number tandem repeat (VNTR) typing method, to identify and distinguish the M. bovis isolates from Gyeonggi-do, Korea. From 2003 to 2004, 59 M. bovis clinical strains were isolated from dairy cattle in Gyeonggi-do, Korea, and these cattle had tuberculosis-like lesions. Twenty-four published MIRU-VNTR markers were applied to the M. bovis isolates and ten of them showed allelic diversity. The most discriminatory locus for the M. bovis isolates in Korea was QUB 3336 (h = 0.64). QUB 26 and MIRU 31 also showed high discriminative power (h = 0.35). The allelic diversity by the combination of all VNTR loci was 0.86. Six loci (MIRU 31, ETR-A and QUB-18, -26, -3232, -3336) displayed valuable allelic diversity. Twelve genotypes were identified from the 59 M. bovis isolates that originated from 20 cattle farms that were dispersed throughout the region of Gyenggi-do. Two genotypes [designation index (d.i.) = e, g] showed the highest prevalence (20% of the total farms). For the multiple outbreaks on three farms, two successive outbreaks were caused by the same genotype at two farms. Interestingly, the third outbreak at one farm was caused by both a new genotype and a previous genotype. In conclusion, this study suggests that MIRU-VNTR typing is useful to identify and distinguish the M. bovis isolates from Gyeonggi-do, Korea.     

The potential for zoonotic transmission of Giardia duodenalis and Cryptosporidium spp. from beef and dairy cattle in Ontario, Canada

The objective of this study was to compare the occurrence and the genotypes and species of Giardia duodenalis and Cryptosporidium spp. in beef and dairy cattle from farms in the Regional Municipality of Waterloo, Ontario, in an effort to determine the potential for zoonotic transmission from these animals. Pooled manure samples were collected from 45 dairy cattle farms and 30 beef cattle farms. The presence of Giardia cysts and Cryptosporidium oocysts was determined by immunofluorescence microscopy, while nested-PCR and DNA sequencing were used to determine genotypes and species. The overall farm prevalence was very high for both Giardia and Cryptosporidium, and was similar for dairy cattle farms (96 and 64%, respectively) and beef cattle farms (97 and 63%, respectively). However, on dairy cattle farms, G. duodenalis and Cryptosporidium spp. were detected in 44% and 6% of total pooled pen manure samples, respectively, with the occurrence of both parasites being generally higher in calves than in older animals. Most Giardia isolates were identified as either the host-adapted genotype G. duodenalis Assemblage E or the zoonotic Assemblage B. Cryptosporidium parvum and Cryptosporidium andersoni were the most frequently identified species in dairy cattle, while the non-zoonotic species Cryptosporidium ryanae and Cryptosporidium bovis were also found. On beef cattle farms, 72% and 27% of the total pooled pen manure samples were positive for Giardia and Cryptosporidium, respectively, with no obvious correlation with age. All Giardia isolates in beef cattle were identified as G. duodenalis Assemblage E, while all Cryptosporidium isolates were identified by sequence analysis as C. andersoni, although microscopic analyses, and subsequent restriction fragment length polymorphism analyses, indicated that other Cryptosporidium species were also present. The results of this study indicate that although Giardia and Cryptosporidium were identified in a higher overall percentage of the pooled beef cattle manure samples than in dairy cattle, firmly established zoonotic genotypes and species were much more common in dairy cattle than in beef cattle in this region. Dairy cattle, and especially dairy calves, may, therefore, pose a greater risk of infection to humans than beef cattle. However, these results may also provide evidence of potential zooanthroponotic transmission (human to animal).     

Serotypes and analysis of distribution of Shiga toxin producing Escherichia coli from cattle and sheep in the lower North Island, New Zealand

AIMS: To serotype a subset of Shiga toxin-producing Escherichia coli (STEC) isolates from cattle and sheep to determine whether any corresponding serotypes have been implicated in human diarrhoeal disease, both in New Zealand and worldwide, and to examine the distribution of STEC and enteropathogenic Escherichia coli (EPEC) amongst cattle (calves, heifers and dairy) and sheep (lambs, rams and ewes), to assess whether carriage of identified bacterial genotypes may be associated with a particular age of animal. METHODS: Recto-anal mucosal swabs (RAMS) were taken from 91 calves, 24 heifers and 72 dairy cattle, and 46 lambs, 50 ewes and 36 rams, from four sites in the Manawatu and Rangitikei regions of New Zealand. Strains of E. coli selected from primary isolation plates were subjected to a multiplex polymerase chain reaction (PCR), to determine the presence of Shiga toxin genes (stx1 and stx2) and the E. coli attaching and effacing gene (eae). RESULTS: Overall, 186/319 (58.3%) animals sampled were positive for stx1, stx2, or eae isolates. More sheep (43.9%) were stx1-positive than cattle (2.7%; p = 0.036), and amongst sheep more lambs and ewes were stx1-positive than rams (p = 0.036). Amongst cattle, more calves and heifers were eae-positive than dairy cows (p = 0.030). Two or more different STEC were isolated from at least 28 (9%) animals (three cattle and 25 sheep), based on their stx/eae genotype. Enterohaemolysin genes were found in 39/51 (76%) isolates serotyped. Twenty-one different serotypes were detected, including O5:H-, O9:H51, O26:H11, O84:H-/H2 and O149:H8 from cattle, and O26:H11, O65:H-, O75:H8, O84:H-, O91:H-, O128:H2 and O174:H8 from sheep; O84:H-, O26:H11, O5:H-, O91:H- and O128:H2 serotypes have been associated with human disease. CONCLUSIONS: If nationally representative, this study confirms that cattle and sheep in New Zealand may be a major reservoir of STEC serotypes that have been recognised as causative agents of diarrhoeal disease in humans. Distribution of STEC and EPEC in cattle and sheep indicates that direct contact with, in particular, calves or their faeces, or exposure to environments cross contaminated with ruminant faeces, may represent an increased risk factor for human disease in New Zealand.     

Unique genotypes of Mycobacterium avium subsp. paratuberculosis strains of Type III

Mycobacterium avium subsp. paratuberculosis (MAP) strains with two new IS900 restriction fragment length polymorphism (RFLP) BstEII types intermediate suspected to belong to the MAP Type III group were isolated from migrating sheep in Germany. Such strains have only been sporadically identified in a few studies. For a better understanding of the genomic diversity of MAP with regard to specific host associations, geographic origin, and the discussed classification into Type I, Type II and Type III, these isolates were further characterized.Using IS900-RFLP, the isolates showed unique fingerprint patterns after BstEII-, PstI-, PvuII- and BamHI-digestion which had not been published before. Additionally, using gyrB-PCR-restriction endonuclease analysis (PCR/REA) and mycobacterial interspersed repetitive unit (MIRU)-PCR, the two strains showed differences to known patterns of the Type I as well as the Type II group. Unique genotypes were also obtained with multilocus short sequence repeat (MLSSR) sequencing and MIRU-variable-number tandem-repeat (VNTR) typing.As expected, genomic profiles identical to the Type I and different from the Type II group were detected by IS1311-PCR/REA, IS1311 sequencing as well as by Large Sequence Polymorphism analysis (LSP^A 8, 17, 20, 4-II, and 18).In addition to distinct growth characteristics, the unique genotypes of the studied sheep strains support their affiliation to the assumed third group within the MAP subspecies and suggest the existence of different genotypes within this Type III group. The results could serve as further evidence that Type I and Type III groups are more closely related to each other than to the bovine Type II group.     

Spatial differences in occurrence of paratuberculosis in Danish dairy herds and in control programme participation

Paratuberculosis is a chronic infection of economic importance to the cattle industry and a voluntary control programme is offered to Danish dairy farmers. Our objective was to evaluate spatial differences in both control programme participation and paratuberculosis prevalence in Denmark. The study included 4414 dairy herds: 1249 were participating in the control programme, and 1503 were tested for antibodies to Mycobacterium avium subsp. paratuberculosis (MAP). Spatial differences were evaluated by kernel smoothing, kriging, and cluster analysis. Participation was lowest among herds on the island Zealand (≤23%). The risk of a herd being infected with MAP was found to be high on most of Zealand, but the uncertainty of this result was large due to a limited number of tested herds. In the rest of the country, the south western part of the peninsula Jutland had the highest risk of MAP (≥91%). The risk of MAP was also high (86-91%) in the northern part of both Jutland and Funen. The predicted apparent within-herd prevalence was highest (5-8.5%) in some local areas across Jutland, in the north western part of the island Funen, and in the south and western part of Zealand. Scan statistics located the primary cluster of herds with high apparent within-herd prevalence in the western part of Funen. Furthermore, a number of significant clusters were found in Jutland and a single significant cluster in Zealand. Consistency was found between kriging and scan statistics results with respect to location of areas with high apparent within-herd prevalence of MAP. Potential explanations for differences in participation include herd size and local herd health advisers, whereas for example soil characteristics might influence prevalence. Further studies are needed to evaluate these and other risk factors.     

Shiga toxin-producing Escherichia coli (STEC) isolated from healthy dairy cattle in southern Brazil

Over a period of 1 year, the production of verotoxin was investigated in 1127 Escherichia coli isolated from 243 dairy cattle from 60 small farms in southern Brazil. Vero cell assay was used to detect toxins in culture supernatants from E. coli isolated from bovine feces. Shiga toxin-producing E. coli (STEC) detection rates were 95% (57 of 60) for farms and 49% (119 of 243) for cattle. Prevalence of STEC-positive cattle in the farms ranged from 0 to 100%. Ninety-six percent (315 of 327) of the STEC isolates did not react in the panel of sera used for typing. Twelve isolates, all non-motile, belonged to serogroups previously associated with human diseases, and 67% (8 of 12) were of only two serotypes (O91:H- and sorbitol-fermenting O157:H-). These results indicate that dairy cattle from the region surveyed may be a source of STEC potentially pathogenic for humans.     

Occurrence and molecular characterization of Cryptosporidium spp. and Enterocytozoon bieneusi in dairy cattle,beef cattle and water buffaloes in China

Cryptosporidium spp. and Enterocytozoon bieneusi are important protists in a wide range of vertebrate hosts, causing diarrheal diseases. Cattle are considered potential reservoirs of Cryptosporidium infection in humans, although their role in the transmission of E. bieneusi is not clear. In the present work, 793 fecal specimens from dairy cattle, native beef cattle, and water buffaloes on 11 farms in China were examined for the presence of Cryptosporidium spp. and E. bieneusi using nested PCR targeting the small subunit (SSU) rRNA gene of Cryptosporidium spp. and the internal transcribed spacer (ITS) of E. bieneusi. For Cryptosporidium, 144/446 (32.3%) dairy cattle, 44/166 (26.5%) beef cattle, and 43/181 (23.8%) water buffaloes were PCR-positive. Sequence analysis was successful for 213 of the 231 Cryptosporidium-positive isolates; among them 94 had Cryptosporidium andersoni, 61 had Cryptosporidium bovis, 54 had Cryptosporidium ryanae, 2 had a Cryptosporidium suis-like genotype, and 2 had mixed infections of C. bovis and C. ryanae. In dairy and beef cattle, C. andersoni and C. bovis were the most common species, whereas C. ryanae was the dominant species in water buffaloes. The latter species produced SSU rRNA sequences different between cattle and water buffaloes. For E. bieneusi, the infection rate of E. bieneusi in dairy cattle, beef cattle and water buffaloes was 4.9%, 5.4% and 2.2%, respectively. All 35 E. bieneusi-positive specimens were successfully sequenced, revealing the presence of four genotypes: three Group 2 genotypes previously reported in cattle as well as humans (I, J and BEB4) and one Group 1 genotype recently reported in yaks (CHN11). Genotypes I and J were the most common genotypes in dairy and beef cattle, while genotype CHN11 was the only genotype seen in water buffaloes. Thus, the distribution of Cryptosporidium spp. and E. bieneusi in water buffaloes might be different from in dairy and beef cattle in China. These findings indicate that some of the Cryptosporidium species and all four E. bieneusi genotypes identified in bovine animals in the study areas may have zoonotic potential.     

Staphylococcus aureus isolates from dairy cows and humans on a farm differ in coagulase genotype

Staphylococcus aureus is a frequent cause of animal and human infections. The aim of the present study was to test diversity of the populations of S. aureus colonising cattle and humans sharing an infected environment. Eighty-six S. aureus isolates obtained from dairy cows, from people coming into contact with dairy cows on the farm and the other farm personnel were characterized by restriction fragment length polymorphism of the coagulase gene. Molecular analyses identified ten polymorphism types with prevalent presentation of type II in isolates from cow's milk and type IV in isolates from people coming into contact with dairy cows on the farm (the cattlemen) and the other farm personnel. Seven further genotypes were identified among the isolates from the cattlemen. The results indicate that the strains dominating in human population did not equate to the causative agents of bovine mastitis.     

Evaluation of Spoligotyping and MIRU-VNTR for Mycobacterium bovis in Xinjiang, China

Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB) in cattle, is also a pathogen for human and other mammals. In this study, 406 cows were screened for bTB by both single intradermal comparative cervical tuberculin (SICCT) test and IFN-γ assay. 135 M. bovis were isolated from 31 SICCT and IFN-γ double-positive cows in Xinjiang Uygur Autonomous Region of China. Spoligotyping and MIRU-VNTR were evaluated for genotyping, and 4 and 7 genotypes were identified, respectively. A new combination of nine MIRU-VNTR loci was most discriminative for M. bovis clones from Xinjiang. Interestingly, two new spoligotypes (SB1903 and SB1904) and special repeat numbers of three loci (ETR-D, QUB 1895 and QUB 3336) were discovered in this study. These results indicated a specific epidemic conservation in Xinjiang, China. M. bovis strains with the unique genotypes were isolated from the herds maintaining parent cows imported from the bTB-free countries, suggesting a possible transmission from the local breed of Xinjiang brown cattle.     

Comparison of the odds of isolation, genotypes, and in vivo production of major toxins by Clostridium perfringens obtained from the gastrointestinal tract of dairy cows with hemorrhagic bowel syndrome or left-displaced abomasum

OBJECTIVE: To compare the frequency of isolation, genotypes, and in vivo production of major lethal toxins of Clostridium perfringens in adult dairy cows affected with hemorrhagic bowel syndrome (HBS) versus left-displaced abomasum (LDA). DESIGN: Case-control study. ANIMALS: 10 adult dairy cattle with HBS (cases) and 10 adult dairy cattle with LDA matched with cases by herd of origin (controls). PROCEDURE: Samples of gastrointestinal contents were obtained from multiple sites during surgery or necropsy examination. Each sample underwent testing for anaerobic bacteria by use of 3 culture methods. The genotype of isolates of C. perfringens was determined via multiplex polymerase chain reaction assay. Major lethal toxins were detected by use of an ELISA. Data were analyzed with multivariable logistic regression and chi2 analysis. RESULTS: C. perfringens type A and type A with the beta2 gene (A + beta2) were the only genotypes isolated. Isolation of C. perfringens type A and type A + beta2 was 6.56 and 3.3 times as likely, respectively, to occur in samples from cattle with HBS than in cattle with LDA. Alpha toxin was detected in 7 of 36 samples from cases and in 0 of 32 samples from controls. Beta2 toxin was detected in 9 of 36 samples from cases and 0 of 36 samples from controls. CONCLUSIONS AND CLINICAL RELEVANCE: C. perfringens type A and type A + beta2 can be isolated from the gastrointestinal tract with significantly greater odds in cattle with HBS than in herdmates with LDA. Alpha and beta2 toxins were detected in samples from cows with HBS but not from cows with LDA.     

Bayesian kriging of seroprevalence to Mycobacterium avium subspecies paratuberculosis and Neospora caninum in Alberta beef and dairy cattle

Identifying spatial patterns of risk is important in the study of diseases with ecologic causes. Furthermore, relatively complex hierarchical modeling is required to determine how factors that are organized across levels interact, such as how an ecologic cause interacts with farm management and with animal characteristics. The objective of this study was to map the risk for Mycobacterium avium subspecies paratuberculosis (MAP - the causative agent of Johne's disease) and Neospora caninum (NC - the cause of neosporosis) infections in Alberta beef and dairy cattle. This objective utilized Bayesian generalized linear kriging to partition herd effects into a portion attributable to location and a portion that was independent of location. Seropositivity to NC in beef cattle showed strong support for spatial covariance, suggesting that ecologic causes were important for beef cattle but not dairy cattle. There was little evidence of spatial covariance for MAP seropositivity in either beef or dairy cattle.     

Evidence of Mycobacterium avium subsp. paratuberculosis infection in Dutch farmed red deer

Paratuberculosis is a chronic disease in ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Most economic losses due to MAP occur in the dairy industry. However, the infection is not restricted to cattle, but also occurs in other ruminants, such as sheep, goat, and deer. Although deer are of minimal economic importance in The Netherlands, they may constitute a source of infection for the dairy industry. This pilot study was conducted to estimate the prevalence of Johne's disease in farmed red deer in The Netherlands. Serum and faecal samples were collected from 140 animals, originating from 8 different farms. Four of the farms had animals that tested positive for Johne's disease. The within-herd MAP seroprevalence varied between 4.8% and 21.2%. In conclusion, this pilot study provides evidence of MAP infection in the Dutch farmed deer population, and thus there might be a risk of MAP transmission between farmed red deer and dairy cattle.     

Seasonal prevalence of thermophilic Campylobacter infections in dairy cattle and a study of infection of sheep

A total of 273 rectal swabs from dairy cows were cultured for Campylobacter jejuni/coli. The isolation rate was 17/72 (24%), 33/106 (31%) and 11/95 (12%) during summer, autumn and winter respectively. Approximately half of the isolates were C. jejuni and the other half C. coli. The isolates recovered from dairy cows were typed by bacterial restriction endonuclease DNA analysis (BRENDA) and compared with those of sheep. Seventeen different BRENDA patterns were produced by the isolates from dairy cows and six from 27 isolates of sheep. Of these 21 different BRENDA patterns only two were common to sheep and cattle.     

Evaluation of four commercial serum ELISAs for detection of Mycobacterium avium subsp. paratuberculosis infection in dairy cows

During the first 3 months of 2006, a study was performed on four dairy cattle herds with a history of clinical paratuberculosis, to evaluate different enzyme-linked immunosorbent assays (ELISAs). Serum samples obtained from 326 animals were analysed using four ELISAs to detect antibodies to Mycobacterium avium subsp. paratuberculosis (MAP). Kappa (kappa) concordance coefficients in pairwise comparisons of the ELISA outcomes ranged up to 0.22 (linear kappa) and 0.25 (quadratic kappa). When the borderline positives obtained were considered as negatives, kappa values remained low (kappa up to 0.19). Having performed the serological tests, faecal samples were then obtained from 55 animals (including all animals testing positive in two or more ELISAs) from the same herds. Faecal culture and faecal polymerase chain reaction (PCR) for the detection of MAP were negative in all cases. The results indicate that neither the currently available serum ELISAs nor faecal culture and PCR are effective for the early detection of MAP in dairy cattle.     

Comparison of fecal culture and F57 real-time polymerase chain reaction for the detection of Mycobacterium avium subspecies paratuberculosis in Swiss cattle herds with a history of paratuberculosis

Background

Bovine paratuberculosis is an incurable chronic granulomatous enteritis caused by Mycobacterium avium subspecies paratuberculosis (MAP). The prevalence of MAP in the Swiss cattle population is hard to estimate, since only a few cases of clinical paratuberculosis are reported to the Swiss Federal Food Safety and Veterinary Office each year.Fecal samples from 1,339 cattle (855 animals from 12 dairy herds, 484 animals from 11 suckling cow herds, all herds with a history of sporadic paratuberculosis) were investigated by culture and real-time polymerase chain reaction (PCR) for shedding of MAP.

Results

By culture, MAP was detected in 62 of 445 fecal pools (13.9%), whereas PCR detected MAP in 9 of 445 pools (2.0%). All 186 samples of the 62 culture-positive pools were reanalyzed individually. By culture, MAP was grown from 59 individual samples (31.7%), whereas PCR detected MAP in 12 individual samples (6.5%), all of which came from animals showing symptoms of paratuberculosis during the study. Overall, MAP was detected in 10 out of 12 dairy herds (83.3%) and in 8 out of 11 suckling cow herds (72.7%).

Conclusions

There is a serious clinically inapparent MAP reservoir in the Swiss cattle population. PCR cannot replace culture to identify individual MAP shedders but is suitable to identify MAP-infected herds, given that the amount of MAP shed in feces is increasing in diseased animals or in animals in the phase of transition to clinical disease.     

Effects of infectious young stock on results of certification, surveillance and control programmes for paratuberculosis in dairy herds

In many epidemiological models for paratuberculosis, it is assumed that infected young stock (<2 years of age) do not shed Mycobacterium avium subsp. paratuberculosis (MAP) before adulthood. If this assumption were true, the effective separation of young stock from adult cattle (≥ 2 years) would largely prevent postnatal infections, provided that uninfected adult cattle are highly resistant to infection. However, this assumption is in contrast with observed faecal shedding of MAP in young stock. Consequently, this assumption may have resulted in an underestimation of the effects of MAP transmission in herds participating in certification-, surveillance-, and control programmes for paratuberculosis. Therefore, the aim of the present study was to evaluate the long-term effects of transmission of MAP amongst young stock on key output parameters of certification-, surveillance-, and control programmes for paratuberculosis in simulated closed dairy herds. Closed Dutch dairy herds participating in a paratuberculosis programme were simulated with a stochastic model, JohneSSim. Various test schemes, preventive management measures, distributions of age at onset of faecal shedding and rates of effective contacts between young stock were simulated. The results indicate that transmission of MAP amongst young stock has no relevant effects on the animal-level prevalence and milk quality of herds that are certified in a paratuberculosis programme. However, transmission of MAP amongst young stock increased the economic losses due to paratuberculosis and costs of participation in a programme. Moreover, it substantially decreased the beneficial effect of the separation of young stock from adult cattle on the probability of being certified. However, even in the presence of transmission of MAP amongst young stock, preventive management measures to separate young stock from adult cattle remain important.     

Seroprevalence of Mycobacterium avium subspecies paratuberculosis, Neospora caninum, Bovine leukemia virus, and Bovine viral diarrhea virus infection among dairy cattle and herds in Alberta and agroecological risk factors associated with seropositivity

A province-wide, cross-sectional seroprevalence and agroecological risk factor study of Mycobacterium avium subspecies paratuberculosis (MAP), Neospora caninum (NC), Bovine leukemia virus (BLV), and Bovine viral diarrhea virus (BVDv) genotypes 1 and 2 (BVDv1 and BVDv2) infection in dairy cattle herds in Alberta was conducted. Among adults, the seroprevalence of MAP, NC, and BLV was 9.1%, 18.5%, and 26.9%, respectively. For MAP, based on a herd test cutpoint of 2 or more seropositive cows, 58.8% of herds were infected. Herd-level seroprevalence for NC and BLV was 98.7% and 86.7%, respectively, based on a herd-test cutpoint of 1 seropositive cow. Among unvaccinated dairy heifers, the seroprevalence for BVDv1 and BVDv2 infection was 28.4% and 8.9%, respectively, while herd-level infection was 53.4% and 19.7%. Seroprevalence for MAP varied moderately by agroecological region, whereas that for NC, BLV, and BVDv1 and BVDv2 did not. For MAP, aridity and soil pH (correlated features of the region) were also important.