Evaluation of testing strategies to identify infected animals at a single round of testing within dairy herds known to be infected with Mycobacterium avium ssp. paratuberculosis.

As part of a broader control strategy within herds known to be infected with Mycobacterium avium ssp. paratuberculosis (MAP), individual animal testing is generally conducted to identify infected animals for action, usually culling. Opportunities are now available to quantitatively compare different testing strategies (combinations of tests) in known infected herds. This study evaluates the effectiveness, cost, and cost-effectiveness of different testing strategies to identify infected animals at a single round of testing within dairy herds known to be MAP infected. A model was developed, taking account of both within-herd infection dynamics and test performance, to simulate the use of different tests at a single round of testing in a known infected herd. Model inputs included the number of animals at different stages of infection, the sensitivity and specificity of each test, and the costs of testing and culling. Testing strategies included either milk or serum ELISA alone or with fecal culture in series. Model outputs included effectiveness (detection fraction, the proportion of truly infected animals in the herd that are successfully detected by the testing strategy), cost, and cost-effectiveness (testing cost per true positive detected, total cost per true positive detected). Several assumptions were made: MAP was introduced with a single animal and no management interventions were implemented to limit within-herd transmission of MAP before this test. In medium herds, between 7 and 26% of infected animals are detected at a single round of testing, the former using the milk ELISA and fecal culture in series 5 yr after MAP introduction and the latter using fecal culture alone 15 yr after MAP introduction. The combined costs of testing and culling at a single round of testing increases with time since introduction of MAP infection, with culling costs being much greater than testing costs. The cost-effectiveness of testing varied by testing strategy. It was also greater at 5 yr, compared with 10 or 15 yr, since MAP introduction, highlighting the importance of early detection. Future work is needed to evaluate these testing strategies in subsequent rounds of testing as well as accounting for different herd dynamics and different levels of herd biocontainment.

The effect of alternative testing strategies and bio-exclusion practices on Johne's disease risk in test-negative herds.

Herd classification is a key component of national Johne's disease (JD) control programs. Herds are categorized on the basis of test results, and separate sub-programs are followed for test-positive and test-negative herds. However, a test-negative herd result does not necessarily equate to JD freedom for reasons relating to disease pathogenesis and available diagnostic tests. Thus, in several countries, JD control programs define test-negative herds as having a "low risk" of infection below a specified prevalence. However, the approach is qualitative, and little quantitative work is available on herd-level estimates of probability of freedom in test-negative herds. This paper examines the effect over time of alternative testing strategies and bio-exclusion practices on JD risk in test-negative herds. A simulation model was developed in the programming language R. Key model inputs included sensitivity and specificity estimates for 3 individual animal diagnostic tests (serum ELISA, milk ELISA, and fecal culture), design prevalence, testing options, and testing costs. Key model outputs included the probability that infection will be detected if present at the design prevalence or greater (herd sensitivity; SeH), the probability that infection in the herd is either absent or at very low prevalence (i.e., less than the design prevalence; ProbF), the probability of an uninfected herd producing a false-positive result [P(False+)], and mean testing cost (HerdCost) for different testing strategies. The output ProbF can be updated periodically, incorporating data from additional herd testing and information on cattle purchases, and could form the basis for an output-based approach to herd classification. A high ProbF is very difficult to achieve, reflecting the low sensitivity of the evaluated tests. Moreover, ProbF is greatly affected by any risk of introduction of infection, decreasing in herds with poor bio-exclusion practices despite ongoing negative test results. The value of P(False+) was substantial when tests with imperfect specificity were used. Testing strategies can substantially influence testing costs but with little effect on test performance. This study illustrates an output-based approach to herd classification, with potential for national and field applications.

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.

Risk factors for the introduction and within-herd transmission of Mycobacterium avium subspecies paratuberculosis (MAP) infection on 59 Irish dairy herds.

Since 1994, Irish cattle have been exposed to greater risks of acquiring Mycobacterium avium subspecies paratuberculosis (MAP) infection as a consequence of the importation of over 70,000 animals from continental Europe. In recent years, there has been an increase in the number of reported clinical cases of paratuberculosis in Ireland. This study examines the prevalence of factors that promote the introduction and within-herd transmission of Mycobacterium avium subspecies paratuberculosis (MAP) on selected Irish dairy farms in the Cork region, and the association between these factors and the results of MAP screening tests on milk sock filter residue (MFR). A total of 59 dairy farms, selected using non-random methods but apparently free of endemic paratuberculosis, were enrolled into the study. A questionnaire was used to collect data about risk factors for MAP introduction and transmission. The MFR was assessed on six occasions over 24 months for the presence of MAP, using culture and immunomagnetic separation prior to polymerase chain reaction (IMS-PCR). Furthermore, blood samples from all entire male and female animals over one year of age in 20 herds were tested by ELISA. Eighteen (31%) farms had operated as closed herds since 1994, 28 (47%) had purchased from multiple sources and 14 (24%) had either direct or indirect (progeny) contact with imported animals. Milk and colostrum were mixed on 51% of farms, while 88% of farms fed pooled milk. Thirty (51%) herds tested negative to MFR culture and IMS-PCR, 12 (20%) were MFR culture positive, 26 (44%) were IMS-PCR positive and seven (12%) were both culture and IMS-PCR positive. The probability of a positive MFR culture was significantly associated with reduced attendance at calving, and with increased use of individual calf pens and increased (but not significantly) if mulitiple suckling was practised. There was poor agreement between MFR culture and MFR IMS-PCR results, but moderate agreement between MFR culture and ELISA test results. This study highlights a lack of awareness among Irish dairy farmers about the effect of inadequate biosecurity on MAP introduction. Furthermore, within-herd transmission will be facilitated by traditional calf rearing and waste management practices. The findings of viable MAP in the presence of known transmission factors in non-clinically affected herds could be a prelude to long-term problems for the Irish cattle and agri-business generally.

An outcomes assessment of intra-articular calcaneal fractures, using patient and physician's assessment profiles.

Thirty-six patients with intra-articular displaced calcaneal fractures were examined to determine both physician- and patient-based outcomes. Three groups were selected. Group A was treated with open reduction and internal fixation, group B was treated with open reduction internal fixation and supplemental bone graft augmentation and the patients in group C were treated with plaster cast immobilisation and no formal operative treatment. All cohorts were well matched for age, sex and severity of injury. Patients were evaluated using both the American Foot and Ankle Society Scoring System (AFASS) and the short form 36 (SF-36). Minimum time to follow up was 4 years. No significant difference was observed between the three groups with regards to pain and functional outcomes using the AFASS score (P>0.05). No difference was observed between the three groups using the SF-36 score (P>0.1). A statistically significant difference was observed, using radiological criteria, between both groups A and B when compared to the non-operative group C. The rate of wound infection in groups A and B was 31.5%. No correlation was found between the SF-36 score and the AFASS score. No correlation was found between the radiological score and either the SF-36 or the AFASS score. This study has found that the conservative treatment of calcaneal fractures can produce satisfactory outcomes with lower morbidity than surgically treated fractures.

The biomechanical evaluation of polyester as a tension band for the internal fixation of patellar fractures.

We use a braided polyester suture in place of cerclage wire in tension band fixations. The objective of this study was to test the biomechanical properties of this technique. Sixteen cadaveric patellae were fractured and repaired by modified tension band fixation. Eight were fixed using eighteen gauge stainless steel wire as a tension band and eight using braided polyester. All specimens were subjected to tensile testing. Polyester was 75.0% as strong as wire. For dynamic testing, the patellae of seven cadaveric knees were fractured and then fixed with polyester tension bands. These were mounted in a device capable of extending the knees from 90 degrees to neutral against an applied force. None of the fixations failed. Three of the specimens fixed using 18 gauge stainless steel wire were compared with three fixed using polyester over 2000 cycles of knee flexion and extension. Polyester performed as well as wire. We conclude that polyester is an acceptable alternative to wire in tension band fixation.

Damage to the superior gluteal nerve after the Hardinge approach to the hip.

We studied prospectively 81 consecutive patients undergoing hip surgery using the Hardinge (1982) approach. The abductor muscles of the hip in these patients were assessed electrophysiologically and clinically by the modified Trendelenburg test. Power was measured using a force plate. We performed assessment at two weeks, and at three and nine months after operation. At two weeks we found that 19 patients (23%) showed evidence of damage to the superior gluteal nerve. By three months, five of these had recovered. The nine patients with complete denervation at three months showed no signs of recovery when reassessed at nine months. Persistent damage to the nerve was associated with a positive Trendelenburg test.

Proprioception in the cruciate deficient knee.

Proprioception was measured in the knees of 20 subjects with instability of the anterior cruciate ligament and compared with 17 age-matched control subjects. There was diminished position sense and threshold for movement detection in the injured patients compared with the control group. The proprioceptive deficit recorded from the injured knee showed a significant correlation with the hamstring/quadriceps power ratio recorded from the injured leg.

Percutaneous screw fixation of tibial plateau fractures.

A series of 13 patients with displaced fractures of the tibial plateau treated by closed reduction and percutaneous pinning have been reviewed 17 months after surgery. All the operations were performed using image intensification to aid reduction of the fracture by ligamentotaxis and to guide screw placement. In two cases, arthroscopy was used in addition to facilitate elevation of the articular surface using a probe inserted through a cortical window in the proximal tibial metaphysis. The postoperative rehabilitation programme consisted of early mobilization and non-weight bearing for at least 2 months. Of the patients, 11 had a satisfactory result, one patient had a fair result with persistent pain and the other had a poor result when the fixation failed in a comminuted bicondylar fracture in porotic bone. This technique is minimally invasive and avoids many of the complications of both conservative and operative treatment and will have an expanding role to play in the management of these fractures.

Vertebral osteomyelitis caused by fusobacterium nucleatum: a case report.

A 58-year-old man with a history of chronic alcohol abuse presented with vertebral osteomyelitis caused by Fusobacterium nucleatum. This case demonstrated the foul smelling abscess characteristic of anaerobic infection. Deep anaerobic infections are well known to be resistant to closed treatment, and the computerized tomographic scan confirmed the diagnosis of a paravertebral abscess in this case. An increased awareness among clinicians that anaerobic bacilli can cause oteomyelitis, together with more sophisticated culture techniques, will greatly aid the management of this virulent form of osteomyelitis.

Sarcoidosis presenting as a wrist tumour.

A forty-year-old male with a painless, indurated mass on the volar surface of the wrist, was proved to have Boeck's Sarcoid. The surgery and pathology of the mass is described and the literature reviewed.

Hemihypertrophy of lower extremity associated with multifocal intraosseous hemangioma.

This is a case report of a child with hemangioma of the bones of the lower extremities. The evolution of the disease in several bones, during the period between infancy and maturity, and serial growth studies of the extremities and differences in length of bones reveals that in some cases the involved bone grew longer than its fellow, whereas in others it grew shorter. Histological examination of an epiphyseal plate demonstrates that hemangioma grew on either side of the plate.