A review of prevalences of paratuberculosis in farmed animals in Europe

Prevalence estimates are used by decision makers such as policy makers and risk assessors to make choices related to certain diseases and infections. Paratuberculosis, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic infection particularly resulting in economic losses among farmed ruminants. Therefore, this infection is of concern for many farming industry decision makers. As a result, multiple studies have been carried out to determine the within-herd and between-herd prevalence of MAP infections. The objective of the present study was to conduct a review and, if possible, compare animal and herd level prevalences of MAP among farmed animals in Europe. European data on prevalences of MAP in all farmed animal species were included from a review of literature. Information on target population and study design, tests used and apparent prevalences were recorded, and subsequently true prevalences were calculated when possible. A critical review of the included studies indicated that although a wide range of studies have been conducted, likely and comparable true prevalence estimates could rarely be calculated. Based on a few studies where the prevalences appeared to be plausible, it was concluded that prevalences of MAP would have to be guesstimates based on available data. The true prevalence among cattle appeared to be approximately 20% and was at least 3-5% in several countries. Between-herd prevalence guesstimates appeared to be >50%. No countries had published sufficient information to claim freedom from MAP or just a near-zero prevalence of MAP infections. No within-flock prevalence estimates were available for goats and sheep. The between-flock prevalence guesstimates were >20%, based only on estimates from Switzerland and Spain. Major critical issues were identified in the majority of the studies, primarily due to lack of knowledge of the test accuracy of the diagnostic test used, or due to studies where the study population did not reflect the target population. Because most of the reported studies did not yield prevalence estimates which were comparable to other studies, there is a continuing need for well-designed studies of the prevalence of MAP infections.     

Ante mortem diagnosis of paratuberculosis: a review of accuracies of ELISA, interferon-gamma assay and faecal culture techniques

Infections with Mycobacterium avium subsp. paratuberculosis (MAP) can be latent for years without affecting the animal, but the animal may become infectious or clinical at some point. Diagnosis of paratuberculosis can be a challenge primarily in latent stages of the infection, and different diagnosis interpretations are usually required by the variety of decision makers. The objective of this paper was to provide a critical review of reported accuracies of ELISA tests, interferon-gamma assays (IFN-gamma) and faecal culture (FC) techniques used for diagnosis of three defined target conditions: MAP infected, MAP infectious and MAP affected animals. For each animal species, target condition and diagnostic test-type, sensitivities (Se) and specificities (Sp) were summarised based on a systematic, critical review of information in literature databases. The diagnostic test information often varied substantially for tests of the same type and make, particularly ELISA, which was the most frequently reported test-type. Comparison of the various tests accuracies was generally not possible, but stratification of test-evaluations by target condition improved the interpretation of the test accuracies. Infectious and affected animals can often be detected, but Se for infected animals is generally low. A main conclusion of the review was that the quality of design, implementation and reporting of evaluations of tests for paratuberculosis is generally poor. Particularly, there is a need for better correspondence between the study population and target population, i.e. the subjects chosen for test evaluation should reflect the distribution of animals in the population where the test is intended to be used.     

Paratuberculosis in a miniature donkey (Equus asinus f. asinus)

Paratuberculosis is mainly an infectious disease of ruminants with worldwide distribution. Infection occurs in early stages of life. Other animal species beyond ruminants are rarely affected, however, experimental and natural infections are possible. A case of paratuberculosis in a miniature donkey (Equus asinus f. asinus) with typical clinical and pathomorphological changes is reported here. Lesions were mainly observed in the intestine. Causative for the profuse diarrhoea with emaciation was massive diffuse granulomatous enteritis involving large quantities of acid-fast organism mainly in macrophages. Granulomatous inflammation with acid-fast bacilli again in macrophages to a lesser degree could be detected in the liver. Mycobacterium avium subsp. paratuberculosis (MAP) was isolated from intestinal contents after an incubation period of four weeks. MAP-specific DNA (IS900 and f57) was detected by polymerase chain reaction in culture material. Additionally MAP-isolates were characterized by multi-target genotyping (MIRU-VNTR- and MLSSR-typing). Isolates belonged to the Type II group and exhibited a unique genotype different from other MAP strains in Germany. The donkey originated from a donkey breeding farm in France with intensive free ranging cattle in the neighbourhood and could have been infected there. Donkeys should be considered as paratuberculosis-susceptible animals in exceptional cases and as possible reservoirs or disseminators of infection.     

Differences in intermittent and continuous fecal shedding patterns between natural and experimental Mycobacterium avium subspecies paratuberculosis infections in cattle

The objective of this paper is to study shedding patterns of cows infected with Mycobacterium avium subsp. paratuberculosis (MAP). While multiple single farm studies of MAP dynamics were reported, there is not large scale meta-analysis of both natural and experimental infections. Large difference in shedding patterns between experimentally and naturally infected cows were observed. Experimental infections are thus probably driven by different pathological mechanisms. For further evaluations of shedding patterns only natural infections were used. Within such infections, the transition to high shedding was studied as a proxy to the development of a clinical disease. The majority of studied cows never developed high shedding levels. Those that do, typically never reduced their shedding level to low or no shedding. Cows that eventually became high shedders showed a pattern of continuous shedding. In contrast, cows with an intermittent shedding pattern had a low probability to ever become high shedders. In addition, cows that start shedding at a younger age (less than three years of age) have a lower hazard of becoming high shedders compared to cows starting to shed at an older age. These data suggest the presence of three categories of immune control. Cows that are intermittent shedders have the infection process under control (no progressive infection). Cows that start shedding persistently at a young age partially control the infection, but eventually will be high shedders (slow progressive infection), while cows that start shedding persistently at an older age cannot effectively control the infection and become high shedders rapidly.     

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.     

Culture of Mycobacterium avium subspecies paratuberculosis (MAP) from blood and extra-intestinal tissues in experimentally infected sheep

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne's disease or paratuberculosis, a chronic enteritis of ruminants, and has been suggested to play a role in Crohn's disease in humans. While Johne's disease is primarily expressed in the gastrointestinal tract, isolation of MAP from extra-intestinal tissues indicates that microbial dissemination via the haematogenous route may occur during the infection. Consequently, the occurrence of mycobacteraemia and dissemination to the liver and hepatic lymph node was investigated in 111 sheep. Disseminated infection was detected in 18 of the 53 sheep that were confirmed to be infected following oral exposure to MAP while the bacterium was isolated from the blood of only 4 of these animals. Disseminated infection was detected more frequently from animals with a positive compared to a negative faecal culture result, multibacillary compared to paucibacillary lesions, and clinical compared to subclinical disease. Detection of MAP in blood by culture was significantly associated with increased time post-exposure and clinical disease, with trends for increased detection in animals with multibacillary lesions and positive faecal culture results. Isolation of MAP from blood was difficult in the early stages of the disease and in paucibacillary animals as the bacteraemia may be intermittent, below the limit of detection or MAP may be present in a dormant non-culturable form. Prolonged incubation periods prior to growth in BACTEC were consistent with inhibition of growth or dormancy in some blood cultures.     

Demographics of cattle positive for Mycobacterium avium subspecies paratuberculosis by faecal culture,from submissions to the Cork Regional Veterinary Laboratory

The demography of bovine infections caused by Mycobacterium avium subspecies paratuberculosis (MAP) in Ireland is poorly defined. The objective of this study was to describe the demographics of cattle positive to MAP on faecal culture, based on submissions to the Cork Regional Veterinary Laboratory (Cork RVL) from 1994 to 2006. The study focused on all available faecal samples from adult cattle with non-responsive chronic diarrhoea that were submitted by private veterinary practitioners to Cork RVL for MAP culture. For each MAP-positive by faecal culture animal, data were collated from Cork RVL and Cattle Movement Monitoring Scheme (CMMS) records. Johne's disease (JD) was confirmed in 110 animals from 86 herds by the Cork RVL between 1994 and 2006, with a rate of positive cases between 15% and 18% over last four years of the study. Two breeds (Holstein/Friesian or Limousin) made up 78% of submissions. Movements were assessed for the 57 study animals with available movement information, 90% died within one year of the test and 26% tested positive in the herd they were born into. The study provides preliminary information about movement trends and demographics of animals with MAP positive submissions. Although the study area is restricted, it includes the most intensive (and economically-important) dairy region in Ireland. The demographics of JD infection from the study area are in agreement with international reports. Further work is required to determine demographic trends, incidence and prevalence of JD throughout Ireland. It is hoped this work may contribute to the development of a surveillance strategy for MAP by regional veterinary laboratories.     

Cell membrane receptors on bovine mononuclear phagocytes involved in phagocytosis of Mycobacterium avium subsp paratuberculosis

OBJECTIVE: To determine cell membrane receptors involved in phagocytosis of Mycobacterium avium subsp paratuberculosis (MAP) organisms. SAMPLE POPULATION: Monocytes were obtained from healthy adult Holstein dairy cows that were test negative for MAP infection on the basis of bacteriologic culture of feces and serologic test results. PROCEDURES: Monocytes or bovine macrophage cell line (BoMac) cells were incubated with MAP organisms for 30, 60, or 120 minutes with or without inhibitors of integrins, CD14, or mannose receptors. Phagocytosis was evaluated by light microscopy or by flow cytometry. CD11a/CD18, CD11b, and CD14 expression on monocytes and BoMac cells was evaluated by use of flow cytometry. RESULTS: Monocytes and BoMac cells rapidly phagocytized MAP organisms. However, compared with BoMac cells, monocytes had a greater total capacity to phagocytize MAP organisms. Addition of neutralizing anti-integrin antibodies (anti-CD11a/CD18 and anti-CD11b) substantially inhibited phagocytosis by monocytes during the first 60 minutes of incubation with MAP organisms, but were less effective at 120 minutes of incubation. Anti-CD11a/CD18 and anti-CD11b antibodies were less effective in inhibiting phagocytosis by BoMac cells. Addition of inhibitors of CD14 or mannose receptors also inhibited phagocytosis of MAP by monocytes. Addition of a combination of integrin and mannose inhibitors had an additive effect in reducing phagocytosis, but addition of integrin and CD14 inhibitors did not have an additive effect. CONCLUSIONS AND CLINICAL RELEVANCE: Multiple receptors are involved in phagocytosis of MAP organisms. Although CD11/CD18 receptors appear to be the major receptors used by MAP at early time points, mannose receptors and CD14 also contribute substantially to phagocytosis.     

Comparison of a DNA probe, complement-fixation and indirect immunofluorescence tests for diagnosing Anaplasma marginale in suspected carrier cattle

Most estimates of the prevalence of anaplasmosis have been based on serologic data using the complement-fixation (CF) and/or card agglutination tests. Since these tests are considered to be only about 50 percent reliable for detecting carrier cattle in enzootically stable herds, the need for more sensitive diagnostic tests is widely recognized. The objective in the present study was to compare the sensitivity of the CF test with that of the indirect immunofluorescence (IIF) test and a recently developed DNA probe in determining the prevalence of Anaplasma marginale infection in cattle from an enzootic area. The study herd consisted of 52 8-month-old steers and 13 3-year-old cows of mixed beef breed. All cattle were initially tested for this comparative purpose. All but one animal (one that was a positive reactor as assessed by all three tests, and served as a positive control), were treated with long-acting oxytetracycline in an attempt to clear any carrier infections. Each animal was then retested at 1 month and 2 months post-treatment (PT), in an effort to determine if the DNA probe could be used to evaluate the effectiveness of the drug. Six of the 65 (9.2%) initial serum samples were CF positive. In contrast, 60 (92.3%) and 64 (98.5%) of the samples were positive as assessed with the IIF test and the DNA probe, respectively. The DNA hybridization reactions varied in intensity within the sample population indicating different individual levels of infection. The DNA probe hybridized with two samples taken at 1 month PT, and with two different samples taken at 2 months PT. The mean IIF titers were reduced at both the 1 month and 2 month sampling times. These results suggest that the drug did not eliminate infections in all cattle. Some may have been cleared, but, in any event, the drug did reduce the level of infections below the sensitivity of the DNA probe and interrupted continuity of stimulation of antibody. Therefore, the DNA probe and the IIF test appear to be considerably more sensitive in detecting carrier infections than the CF test, and should be considered in future epidemiologic studies.     

Use of the johnin PPD interferon-gamma assay in control of bovine paratuberculosis

Although the interferon-gamma (IFN-γ) assay for measurements of cell-mediated immune (CMI) responses to paratuberculosis PPD (johnin) has been available for close to 20 years, the assay has not yet emerged as the long desired test to identify infected animals at an early time point. Among other issues, this relates to problematic interpretation of the test results and maybe an over-expectation of what can be deducted from this kind of test given the chronic nature and slow development of infection of paratuberculosis. Over a number of years a modified IFN-γ assay with addition of recombinant bovine IL-12 to the PPDj stimulation of blood samples from the heifer group in more than 20 Danish dairy herds which also perform surveillance of MAP antibodies in milk have been performed. The results indicate that IFN-γ assay results are specific for paratuberculosis, but the IFN-γ assay result of an individual animal cannot establish whether the animal is infected or predict the future progression of disease in this animal. The IFN-γ assay should thus be used on a group of animals to test the level of exposure to paratuberculosis bacteria the animals have experienced, and thereby assist in maintaining rational in-herd management procedures and in the establishment of paratuberculosis status of a given herd. Indeed, for any diagnostic test applied in paratuberculosis, both the diagnostic target condition and the purpose of the diagnostic testing must be considered before any meaningful estimates of sensitivity or specificity can be given.     

Histoplasmosis infection in two cats from California

Systemic mycotic infections are typically localized to specific geographic regions of the country, because the organisms involved have certain environmental requirements for growth. Suspicion of infection relies on travel to or residence in recognized endemic regions. This report describes infection with histoplasmosis in two indoor cats from central California, an area not considered to be endemic for the disease. Systemic mycotic infections should be considered as differential diagnoses in any cat with compatible clinical signs, regardless of travel history or residence, especially if the cat is presented within a recognized endemic region.     

Treatment vs non-treatment of helminth infections in cattle: defining the threshold

Helminth infections are an important cause of lost productivity in livestock world-wide, often necessitating anthelmintic treatment. However, a large part of the anthelmintics are used indiscriminately because the parasite levels are too low to justify treatment or because the treatments are not correctly programmed, resulting in undertreatment or overtreatment. The objective of this paper is to discuss possible thresholds for anthelmintic treatment of some of the more important helminth infections in livestock, i.e. gastrointestinal nematodes, lungworms and liver fluke, to promote a more appropriate use of anthelmintics. When possible, a distinction is made between therapeutic thresholds, production-based thresholds and preventive thresholds. A "therapeutic threshold" is intended to identify (an) animal(s) with parasite levels that necessitate immediate treatment. The therapeutic threshold is basically the diagnosis of clinical disease, and can be determined relatively easily for the parasites discussed in this paper. A "production-based threshold" is intended to measure the effects of sub-clinical parasitism on productivity parameters, such as weight gain and milk yield, before clinical disease occurs. Finally, a "preventive threshold" is meant to predict future infection levels, to enable the application of appropriate control measures.     

Longitudinal data collection of Mycobacterium avium subspecies Paratuberculosis infections in dairy herds: the value of precise field data

Longitudinal infection data on Mycobacterium avium subspecies paratuberculosis (MAP) was collected on three dairy farms in Northeastern United States during approximately 10 years. Precise data on animal characteristics and animal location within farm were collected on these farms. Cows were followed over time with regard to MAP status during biannual fecal and serum sampling and quarterly serum sampling. Approximately 13 000 serum samples, 6500 fecal samples and 2000 tissue samples were collected during these years. Prevalence of positive samples was 1.4% for serological samples, 2.2% in fecal samples and 16.7% in tissue samples. Infection dynamics of MAP was studied and resulted in a number of potential changes in our understanding of MAP infection dynamics. First, a high prevalence of MAP infection was observed in these herds due to lifetime follow up of cows, including slaughter. Second, two distinctly different infection patterns were observed, so called non-progressors and progressors. Non-progressors were characterized by intermittent and low shedding of MAP bacteria and a virtual absence of a humoral immune response. Progressors were characterized by continuous and progressive shedding and a clearly detectable and progressive humoral immune response. Strain typing of MAP isolates on the three farms identified on two of three farms a dominant strain type, indicating that some strains are more successful in terms of transmission and infection progression. Continuous high quality longitudinal data collection turned out to be an essential tool in our understanding of pathobiology and epidemiology of MAP infections in dairy herds.     

Progress towards understanding the spread, detection and control of Mycobacterium avium subsp paratuberculosis in animal populations

OBJECTIVE: To review and interpret aspects of the pathogenesis and epidemiology of paratuberculosis (Johne's disease) for veterinarians involved in current Johne's disease control programs. PROCEDURE: An electronic and manual search was undertaken to identify published information which, together with limited unpublished data, was interpreted and summarised. CONCLUSIONS: Paratuberculosis, a chronic enteropathy of ruminants, is caused by Mycobacterium avium subsp paratuberculosis and is transmitted mainly in faeces to young animals by infected adults, some of which may not have clinical signs. The incubation period is inversely related to the size of the challenge dose but can be extremely prolonged. Clinical cases may not be seen within the economic lifespan of farm animals, particularly when stocking rates are low, pasture is spelled, or when animals are culled at a relatively young age. Other as yet unknown influences may determine the rate of progression or recovery from infection. Paratuberculosis appears in a range of forms from a disease with high prevalence and significant mortality through to one with very low prevalence and little obvious morbidity or mortality. Detection of infected flocks and herds relies on use of laboratory tests. Bacteriological culture of faeces is the most sensitive herd-level test. The passage of time and repeated testing are the greatest allies in detecting paratuberculosis because infected animals progress in the disease process and most tests are more effective in the later stages of the disease. These factors generally cause the prevalence of paratuberculosis to be underestimated at both herd or flock and regional level. Greater understanding of the epidemiology and pathogenesis of M a paratuberculosis infection is critical in order to design improved diagnostic strategies, assess the feasibility of eradication and develop control options, particularly in small ruminants.     

Dairy farmers' reasons for participation in the Danish control programme on bovine paratuberculosis

The Danish dairy industry initiated a voluntary, producer-paid control programme on Mycobacterium avium subsp. paratuberculosis (MAP) in 2006. Approximately 28% of the dairy herds, including 40% of the cows, are part of the programme. Farmers' reasons for participation are of great importance for the success of voluntary disease control programmes. This study was carried out to determine these reasons. Questionnaires with seven close-ended questions were mailed to the 1177 voluntary participants in 2008. A total of 1013 (86%) responded, and multiple reasons could be given by each farmer. The distribution of reasons for participation in the programme was: (1) control to increase animal health (91%); (2) certification "free of MAP infection" within 4-10 years (87%); (3) control to avoid production losses associated with MAP infections (86%); (4) control of MAP infections to increase consumer safety (64%); (5) certification for sale of livestock (58%); (6) control following production losses (48%); and (7) certification "free of MAP infection" within 1-3 years (31%). It was not possible to rank the reasons for participation since weighting of responses was not included. Therefore, the relative importance of the reasons given could not be determined. Based on the farmers' responses, control of MAP infections to increase animal health and avoid production losses were frequent reasons for participating in the Danish paratuberculosis control programme. The results also indicate that implementation of a certification programme would be desired by farmers. Animal health advisors should consider the diversity of participation reasons and address the specific reasons of individual farmers when establishing a strategy for control of MAP infections in a herd.     

Trends and advances in the diagnosis and control of paratuberculosis in domestic livestock

Paratuberculosis (pTB) is a chronic granulomatous enteritis caused by Mycobacterium avium subsp. paratuberculosis (MAP) in a wide variety of domestic and wild animals. Control of pTB is difficult due to the lack of sensitive, efficacious and cost-effective diagnostics and marker vaccines. Microscopy, culture, and PCR have been used for the screening of MAP infection in animals for quite a long time. Besides, giving variable sensitivity and specificity, these tests have not been considered ideal for large-scale screening of domestic livestock. Serological tests like ELISA easily detects anti-MAP antibodies. However, it cannot differentiate between the vaccinated and infected animals. Nanotechnology-based diagnostic tests are underway to improve the sensitivity and specificity. Newer generation diagnostic tests based on recombinant MAP secretory proteins would open new paradigm for the differentiation between infected and vaccinated animals and for early detection of the infection. Due to higher seroreactivity of secretory proteins vis-à-vis cellular proteins, the secretory proteins may be used as marker vaccine, which may aid in the control of pTB infection in animals. Secretory proteins can be potentially used to develop future diagnostics, surveillance and monitoring of the disease progression in animals and the marker vaccine for the control and eradication of pTB.     

Diagnostic tests for small ruminant lentiviruses

Maedi visna virus and caprine arthritis encephalitis virus are closely related retroviruses that cause chronic inflammatory disease in small ruminants. The infections are characterised by insidious onset and slow progression. Diagnosis of infection is usually by serological testing. A variety of assays are available for this purpose, though the relative sensitivity and specificity of these assays has not been compared systematically. Here we review recent developments in laboratory diagnostic methods and their use in field diagnosis. The results suggest that a combination of ELISA and PCR might afford optimal detection of SRLV infection.     

滞育诱导温度和光照节律对家蚕sod基因和cat基因的表达的影响

家蚕(Bombyxmori)是卵滞育性鳞翅目模式昆虫,其滞育性受亲代卵孵化期(催青期)温度、光节律等环境因子诱导。为了研究家蚕滞育与温度和光照节律的关系,本文调查了温度、光照节律对家蚕sod基因和cat基因表达的影响。催青期中除了孵化期,25℃持续光照下(25LL)卵的sodmRNA均保持在较高水平,另外,sod基因在20℃光照黑暗(20LD)12h交替环境下的表达量要高于15℃持续黑暗(15DD)条件,且孵化后期这种现象更加明显。cat基因在25LL、20LD和15DD环境之间的表达量无差异,但是孵化后期(积温2160-3600℃.h),cat基因表达水平显著上调,这与在此阶段的蚕卵胚胎对滞育诱导环境温度和光节律比较敏感的结论相一致。此外,本文还调查了子代卵中sod基因和cat基因的表达情况。sod基因在人工活化卵(DTE)中的表达水平显著高于非浸酸的滞育性卵(DDE);卵龄24-192h,25LL子代卵逐渐进入滞育,sod基因表达量下调。低温黑暗条件会上调家蚕子代卵sod基因的表达水平。在初期的盐酸活化卵(DTE)中,cat表达量低于滞育卵(DDE),而后逐渐上升,直至接近滞育卵表达量,这表明盐酸可能会抑制cat基因表达。在恒温条件下,黑暗条件会促进子代卵上调cat表达。在温度光照协同作用下,20LD子代卵中cat表达量低于25LL和15DD。     

Epidemiologic and clinical aspects of feline immunodeficiency virus infection in cats from the continental United States and Canada and possible mode of transmission

The epidemiologic features of feline immunodeficiency virus (FIV) infection were evaluated in 2,765 cats from the United States and Canada. Of these cats, 2,254 were considered by veterinarians to be at high risk for the infection, and 511 were healthy cats considered to be at low or unknown risk. Of the cats in the high-risk group, 318 (14%) were found to be infected with FIV. The infection rate among low- or unknown-risk cats was 6 of 511 (1.2%). Male cats in the high-risk group were 3 times more likely to be infected than were females, similarly as were cats greater than 6 years old, compared with younger cats; domestic cats, compared with purebred cats; and free-roaming cats, compared with confined cats. Feline immunodeficiency virus and FeLV infections did not appear to be linked with each other; 16% of FeLV-infected cats in the high- and low-risk groups were coinfected with FIV. In contrast, there was a pronounced linkage between FIV and feline syncytium-forming virus (FeSFV) infections. Seventy-four percent of FeSFV-infected cats in the high-risk study group were coinfected with FIV, compared with a 38% FIV infection rate among cats that were not infected with FeSFV. The major clinical manifestations associated with FIV infection in cats that were surveyed included chronic oral cavity infections (56%), chronic upper respiratory tract disease (34%), chronic enteritis (19%), and chronic conjunctivitis (11%). Bacterial infections of the urinary tract (cystitis), skin, and ears were seen in a small proportion of cats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sequential development of histologic lesions and their relationship with bacterial isolation, fecal shedding, and immune responses during progressive stages of experimental infection of lambs with Mycobacterium avium subsp. paratuberculosis

Understanding pathogenesis during progressive stages of infection by Mycobacterium avium subsp. paratuberculosis (MAP) and finding suitable methods for its diagnosis are key to the control of Johne's disease in animals. Paratuberculosis was experimentally produced in 20 crossbred lambs by oral administration of MAP to study the sequential development of lesions between 10 and 330 days postinfection and to assess commonly used diagnostic methods such as bacterial culture, lymphocyte stimulation test (LST), and enzyme-linked immunosorbent assay (ELISA) during progressive stages of infection. Histologic lesions were classified into four grades from grade 1 (least severe) to grade 4 (most severe) on the basis of location of granulomatous lesions in different regions and layers of intestines, their association with intestinal lymphoid tissues, pattern and distribution of lesions, types of cellular infiltration, and presence of acid-fast bacilli. It is evident that infection first establishes in lymphoid tissues of the small intestine, possibly at multiple sites, producing segmental lesions and from there spreads to lamina propria and local lymph nodes. Wide variability in the histologic lesions in relation to postinfection periods and initial tropism of MAP to the intestinal lymphoid tissues (Peyer's patches) suggests a differential susceptibility of young animals, possibly because of compositional phenotypic variation of Peyer's patches influencing subsequent course of infection. Histopathology was found to be a better indicator of paratuberculous infection than bacteriology in sheep. The LST (reflecting the cellular immune response) and ELISA (reflecting the humoral immune response) had overall sensitivities of 65% (11 of 17) and 42% (8 of 19), respectively, in sheep with different types of pathology but when employed together could detect about 88% of infected animals.