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Biomedical subjects

M V Thrusfield

Publications and source records attributed to M V Thrusfield.

At least 19 recordsLinked to original sources

Use and abuse of mathematical models: an illustration from the 2001 foot and mouth disease epidemic in the United Kingdom.

Foot and mouth disease (FMD) is a major threat, not only to countries whose economies rely on agricultural exports, but also to industrialised countries that maintain a healthy domestic livestock industry by eliminating major infectious diseases from their livestock populations. Traditional methods of controlling diseases such as FMD require the rapid detection and slaughter of infected animals, and any susceptible animals with which they may have been in contact, either directly or indirectly. During the 2001 epidemic of FMD in the United Kingdom (UK), this approach was supplemented by a culling policy driven by unvalidated predictive models. The epidemic and its control resulted in the death of approximately ten million animals, public disgust with the magnitude of the slaughter, and political resolve to adopt alternative options, notably including vaccination, to control any future epidemics. The UK experience provides a salutary warning of how models can be abused in the interests of scientific opportunism.

Animal Welfare↗

A review of foot-and-mouth disease with special consideration for the clinical and epidemiological factors relevant to predictive modelling of the disease.

Modelling the epidemiology of foot-and-mouth disease (FMD) has been undertaken since the early 1970s. We review here clinical factors and modelling procedures that have been used in the past, differentiating between those that have proved to be more relevant in controlling FMD epidemics, and those that have showed less significance. During the 2001 UK FMD epidemic, many previously developed FMD models were available for consideration and use. Accurate epidemiological models can become useful tools for determining relevant control policies for different scenarios and, conversely, inaccurate models may become an abuse for disease control. Inaccuracy presents two opposing difficulties. Firstly, too much control (in terms of animal slaughter for 2001) would negatively impact the farming community for many subsequent years, whilst too little control would permit an epidemic to persist. Accuracy however, presents the optimal permutation of control measures that could be implemented for a given set of conditions, and is a prerequisite to boosting public confidence in the use of epidemiological models for future epidemics.

Animals↗

Randomised, controlled field trial of two new techniques for the castration and tail docking of lambs less than two days of age.

Two methods to reduce the pain associated with the castration and tail docking of lambs with rubber rings were tested by 10 shepherds, each using 60 housed lambs. In 20 of the lambs the innervation to the scrotum, testes and tail was crushed with a 'Big Nipper' bloodless castrator, and in 20 local anaesthetic (2 per cent lignocaine with adrenaline) was injected with a newly developed high-pressure jet injector under the rubber rings after they had been applied; 10 lambs were given a placebo treatment and 10 were treated by the shepherds' routine elastrator ring procedure. Both new methods significantly decreased the incidence of limb and tail movement by 78 per cent and the time spent by the lambs in abnormal postures, when compared with either the shepherds' routine treatment or the placebo treatment. An experienced observer and most of the shepherds also assessed that the lambs suffered signficantly less pain when treated by the two new methods than when they were treated with rubber rings alone. No detrimental long-term effects of the two new methods were observed. On average the new methods took 68 seconds to apply, compared with 29 seconds for the rubber rings; of the two new methods most shepherds preferred using the pressure jet injector.

Amputation, Surgical↗

Response of pheasants to live attenuated turkey rhinotracheitis vaccine.

The entire crop of 18,120 pheasants for the 2000 rearing season (May 8 to August 7) of one estate in the south of England was vaccinated at one day and five weeks of age with a turkey rhinotracheitis (TRT) vaccine. Blood samples and oropharyngeal swabs were taken from the second week's hatching every three weeks throughout the growing season to assess the response of the birds. There was evidence of seroconversion in samples collected three weeks after vaccination, with positive titres being maintained in 33 per cent or more of the population up to at least 22 weeks of age. Positive titres were also recorded in samples taken on December 6 from shot birds between 22 and 30 weeks of age. Positive titres to infectious bronchitis virus (IBV) were identified in a high proportion of the poults as early as one day of age. Reverse-transcriptase PCR detected IBV-like virus and TRT of the same subtype as the TRT vaccine administered three weeks previously.

Animals↗

'Battered pets': features that raise suspicion of non-accidental injury.

A study of veterinarians' perceptions, and experience, of non-accidental injury (NAI) to pets was undertaken using an anonymous questionnaire distributed to a random sample of 1000 small animal practitioners in the UK. NAI was acknowledged by 91.3 per cent (95 per cent confidence interval, 88.2 to 93.9 per cent) of the 404 respondents who returned questionnaires, of whom 48.3 per cent (95 per cent confidence interval, 43.4 to 53.1 per cent) had either suspected or seen NAI. Four hundred and forty-eight cases were documented, predominantly in dogs (243) and cats (182). Factors either raising suspicion, or facilitating recognition, of NAI included: implication of a particular person, features of the history, referral agency involvement, behaviour of the owner and/or the animal, nature of the injuries, and socioeconomic class of owners. Additionally, sexual abuse and suspected cases of Munchausen syndrome by proxy were recorded.

Animals↗

'Battered pets': non-accidental physical injuries found in dogs and cats.

Records of 243 cases of non-accidental injury (NAI) in dogs, and 182 cases in cats, submitted by a sample of small animal practitioners in the UK, revealed a wide range of injuries. These included bruises, fractures, repetitive injuries, burns and scalds, stab and incised wounds, poisoning, asphyxiation and drowning (which showed remarkable similarities to NAI in children), as well as sexual abuse and injuries specifically caused by firearms. Traumatic skeletal injuries in the dogs were more commonly found in the anterior part of the skeleton, in comparison with those resulting from road traffic accidents. Young male dogs and young cats were particularly at risk of NAI. A moderately increased risk was identified in the Staffordshire bull terrier, cross-breed dogs and the domestic shorthaired cat, whereas the Labrador retriever showed a decreased risk. No single injury or group of injuries, when divorced from the circumstances surrounding a suspect case, could be considered to indicate, conclusively, NAI. Repetitive injuries, however, were highly suggestive of NAI.

Animals↗

'Battered pets': sexual abuse.

A study of non-accidental injury in small animals in the UK, based on responses from a random sample of small animal practitioners, identified 6 per cent of the 448 reported cases as being sexual in nature. Twenty-one cases occurred in dogs, five in cats and two in unspecified species. Reasons for suspecting sexual abuse were: the type of injury; behaviour of the owner; statements from witnesses; and admission by the perpetrator. Types of injury included vaginal and anorectal penetrative (penile and non-penile) injury, perianal damage, and trauma to the genitals. Some injuries (such as castration) were extreme, and some were fatal. In contrast, other cases revealed no obvious damage. The type and severity of injuries were similar to those described in texts on child abuse and human forensic pathology.

Animals↗

'Battered pets': Munchausen syndrome by proxy (factitious illness by proxy).

Nine cases of suspected Munchausen syndrome by proxy (MSBP), involving pets as proxies, were identified among 448 cases of non-accidental injury to small animals. These cases, recorded by a random sample of small animal practitioners in the UK, demonstrated several combinations of features, including attention-seeking behaviour by the owner, real and apparently factitious clinical signs, deliberate injury, markedly abnormal biochemical profiles, serial incidents, interference with surgical sites, recovery after separation from the owner, and 'veterinarian-shopping' by the owner. All of these features are consistent with those identified in the well documented MSBP in which children are the victims. Furthermore, one of the cases involved serial attempts at poisoning other animals and a child.

Animals↗

The occurrence of Trypanosoma evansi in buffaloes in Indonesia, estimated using various diagnostic tests.

The prevalence and incidence of Trypanosoma evansi infections in village buffaloes in Central Java were estimated using parasitological tests, two antigen-detection ELISAs (2G6 Ag-ELISA and Tr7 Ag-ELISA), an antibody-detection ELISA (IgG ELISA) and a card agglutination test (CATT). Of 2387 village buffaloes tested in five districts, 4 % (95 % confidence interval [CI]: 3 %, 5 %) were positive with the microhaematocrit test (MHCT), 58 % (95 % CI: 56 %, 60 %) were positive with the 2G6 Ag-ELISA and 70 % (95 % CI: 68 %, 72 %) were positive with the Tr7 Ag-ELISA. An increasing prevalence with age was found and the proportion of positive buffaloes was highest in the over 84 months-old age-group (68 %) with the 2G6 Ag-ELISA and in the 37-60 months-old age-group (78 %) with the Tr7 Ag-ELISA. Parasitaemic buffaloes were found in more than half of the villages visited. Corrected village-specific prevalence values obtained with the two Ag-ELISAs ranged from 0% to over 100%, and prevalence differed significantly (P < or = 0.0001) between villages in four of the five districts. Overall, 10% of buffaloes tested in markets were found to be parasitaemic and 39, 56 and 47 % were found positive with the 2G6 Ag-ELISA, IgG ELISA and CATT, respectively. Incidence rates varied according to the test used and ranged from 0.22 (95 % CI: 0.09, 0.44) to 0.44 (95 % CI: 0.24, 0.76), per animal-year at risk, in two villages. The results highlight the importance of using validated diagnostic tests to obtain accurate estimates of prevalence and incidence. These parameters are needed, for example in mathematical models, for the development and evaluation of different control strategies for T. evansi infections in buffaloes.

Animals↗

Evaluation of antigen detection and antibody detection tests for Trypanosoma evansi infections of buffaloes in Indonesia.

Two Ag-ELISAs, an IgG-specific antibody detection ELISA (IgG ELISA) and a card agglutination test (CATT) for the detection of Trypanasoma evansi infections in buffaloes in Indonesia, were compared. Diagnostic sensitivity estimates were obtained by testing sera from 139 Indonesian buffaloes which had been found to be infected by parasitological tests. Diagnostic specificity was estimated by testing sera from 263 buffaloes living in Australia. Response-operating characteristic curves were constructed, and optimal ELISA cut-off values, which minimized the number of false-negative and false-positive results, were chosen. The IgG ELISA had the highest sensitivity (89%) and the CATT had the highest specificity (100%). There was a significant difference between the sensitivities (71 and 81%), but not between the specificities (75 and 78%), of the two Ag-ELISAs. The four tests were further compared by calculation of post-test probabilities of infection for positive and negative test results using a range of prevalence values, and likelihood ratios. The results suggested that the CATT was the best test to 'rule-in' infection (i.e. the highest probability of infection in test-positive animals) and the IgG ELISA was the best test to 'rule-out' infection (i.e. the lowest probability of infection in test-negative animals).

Agglutination Tests↗

Associations between age, parity, hormonal therapy and breed, and pyometra in Finnish dogs.

A case-control study of 953 dogs with pyometra and 10,660 unmatched control dogs was used to investigate the relationships between age, parity, hormonal therapy and breed, and pyometra in Finnish dogs. Cases were reported in animals between nine months and 18 years of age, with a median age at diagnosis of nine years. Nulliparous bitches had a moderately higher risk of developing pyometra than primiparous and multiparous animals (adjusted odds ratio point estimate, 6.63). The administration of oestrogen increased the risk of pyometra in bitches up to four years of age (odds ratio point estimate > 6). No significant risk-enhancing effect of progestin treatment was detected and it is unlikely that such a risk, if present, is high (likelihood of the odds ratio exceeding 2 < 0.18). Seventeen breeds had an increased risk, and the wire-haired dachshund and mongrels had a decreased risk of developing the condition.

Aging↗

Acquired urinary incontinence in bitches: its incidence and relationship to neutering practices.

A five-year cohort study was conducted on bitches chosen by a sample of 233 randomly selected practising veterinary surgeons in the UK, to estimate the incidence of acquired urinary incontinence (AUI) in neutered and entire animals, and to investigate possible risk factors associated with neutering practices. Information was collected using questionnaires, and data on 809 bitches, of which 22 developed AUI, were obtained. The estimated incidence rates in neutered and entire animals were 0.0174 and 0.0022 per animal-year, respectively (95 per cent confidence intervals: 0.0110, 0.0275 and 0.0009, 0.0058, respectively). The relative risk, neutered vs entire, was 7.8 (95 per cent confidence interval: 2.6, 31.5). The attributable proportion(exposed) and population attributable proportion were 87.1 per cent and 63.1 per cent (95 per cent confidence intervals: 61.9 per cent, 95.6 per cent, and 28.3 percent, 88.5 per cent, respectively). An increased risk, significant at the conventional 5 per cent level, was not demonstrated in animals neutered before, vs after, first heat (relative risk: 3.9, 95 per cent confidence interval: 0.8, 10.4), although the result was significant at the 10 per cent level. Removal of the cervix was not shown to be a risk factor in neutered dogs.

Animals↗

Castration of calves: a study of methods used by farmers in the United Kingdom.

A postal survey of farmers was conducted to determine the main methods used to castrate calves, and by whom and how they were applied. Among the 28 per cent of farmers who replied, those who did castrate calves used one or more of three methods: the Burdizzo was used by 43 per cent of farmers, surgery by 39 per cent, and rubber rings by 32 per cent, with 10 per cent using more than one method. Calves were castrated at all ages from less than one week to over six months, with one third of them being castrated at an age that legally requires the operation to be done under local anaesthesia by a veterinary surgeon. Rubber rings were never used by veterinary surgeons, but they carried out 43 per cent of surgical castrations, which was the method of choice in older calves. Local anaesthetic was used on 15 per cent of farms, mainly for surgical castrations. Sixty-seven per cent of farmers using the Burdizzo applied it twice, with the majority correctly applying the second crush below the first, and 90 per cent used precautions to control infection after surgical castration.

Anesthesia, Local↗

Feline dystocia: prevalence, and association with cranial conformation and breed.

The litter prevalence of feline dystocia was investigated using a questionnaire survey of cat breeders. Information was obtained on 2928 litters, from 735 queens. Dystocia was reported to have occurred in 5.8 per cent of litters. The level of dystocia in individual breeds ranged from 0.4 per cent of litters born in a large colony of cats of mixed breeding, to 18.2 per cent of litters in the Devon rex. Pedigree litters were at significantly higher risk than litters of cats of mixed breeding (odds ratio: 22.6). Relatively high levels of dystocia were identified in Siamese-type, Persian and Devon rex litters, whereas cats of mixed breeding showed a relatively low litter prevalence. Dolicocephalic and brachycephalic types were found to have significantly higher levels of dystocia than mesocephalic cats.

Animals↗

Association in bitches between breed, size, neutering and docking, and acquired urinary incontinence due to incompetence of the urethral sphincter mechanism.

The association in bitches between breed, size, neutering and docking, and acquired incompetence of the urethral sphincter mechanism was investigated. Observational studies were conducted on referred and first-opinion cases of hormonal urinary incontinence and on referred, confirmed cases of incompetence of the urethral sphincter mechanism. Large and giant breeds were at high risk, whereas small breeds were at low risk. Specific breeds at high risk were the old english sheep-dog, rottweiler, dobermann pinscher, weimaraner and Irish setter. The labrador retriever had a relatively low risk. There was also a positive association between docking and neutering, and the two conditions.

Amputation, Surgical↗

Evaluation of enzyme immunoassays in the diagnosis of camel (Camelus dromedarius) trypanosomiasis: a preliminary investigation.

Three enzyme immunoassays were used for the serodiagnosis of Trypanosoma evansi in camels in the Sudan in order to evaluate their ability to discriminate between infected and non-infected animals. Two assays were used for the detection of trypanosomal antibodies, one using specific anti-camel IgG conjugate and another using a non-specific Protein A conjugate. The third assay detected the presence of trypanosomal antigens using anti-T. evansi antibodies in a double antibody sandwich assay. Inspection of the frequency distribution of assay results suggested that the ELISA for circulating trypanosomal antibodies using specific antisera and the ELISA for circulating antigens can distinguish between non-infected camels and infected camels exhibiting patent infections or not. The ELISA using Protein A conjugate to bind non-specifically to camel immunoglobulin did not appear to discriminate between infected and non-infected animals.

Animals↗