The immobilization of the badger (Meles meles)

Evaluation of the anaesthetic effects of combinations of ketamine, medetomidine, romifidine and butorphanol in European badgers (Meles meles)

OBJECTIVE

To evaluate the effects of three anaesthetic combinations in adult European badgers (Meles meles).

STUDY DESIGN

Prospective, randomized, blinded, experimental trial.

ANIMALS

Sixteen captive adult badgers.

METHODS

The badgers were each anaesthetized by intramuscular injection using the three techniques assigned in random order: romifidine 0.18 mg kg(-1), ketamine 10 mg kg(-1) and butorphanol 0.1 mg kg(-1) (RKB); medetomidine 0.1 mg kg(-1), ketamine 9 mg kg(-1) and butorphanol 0.1 mg kg(-1) (MKB); and medetomidine 0.1 mg kg(-1) and ketamine 10 mg kg(-1) (MK). Initial drug doses were calculated based on a body mass of 10 kg. Additional anaesthetic requirements, time to drug effect, duration of action and recovery from anaesthesia were recorded. Heart rate and rhythm, respiratory rate and rhythm, rectal and subcutaneous microchip temperature and oxygen saturation were recorded every 5 minutes. Depth of anaesthesia was assessed using: muscle tone; palpebral and pedal reflexes; and tongue relaxation at these time points. Blood samples and a tracheal aspirate were obtained under anaesthesia. Atipamezole was administered if the badger had not recovered within 60 minutes Parametric data were analysed using anova for repeated measures, and nonparametric data using Friedman's, and Cochran's Q tests: p < 0.05 was considered significant.

RESULTS

All combinations produced good or excellent muscle relaxation throughout the anaesthetic period. RKB had the shortest duration of anaesthesia (16.8 minutes compared with MKB 25.9 minutes and MK 25.5 minutes) and antagonism was not required. RKB depressed respiratory rate less than MK and MKB. There was no significant difference between techniques for heart rate and rhythm.

CONCLUSIONS AND CLINICAL RELEVANCE

All combinations provided anaesthetic conditions suitable for sampling and identification procedures in adult badgers. The RKB protocol provided a significantly shorter period of anaesthesia when compared with the combinations containing medetomidine.

Social organization and movement influence the incidence of bovine tuberculosis in an undisturbed high-density badger Meles meles population

1. The culling of European badgers Meles meles has been a central part of attempts to control bovine tuberculosis (TB) in British cattle for many years. Recent results, however, indicate that this approach could in practice enhance disease spread. 2. This paper looks at the relationship between TB incidence and badger ecology in a high-density population in south-west England, which has been the subject of a long-term intensive study. The principal aims were to relate the probability of TB incidence, as detected by culture of clinical samples (i.e. excretion of bacilli), at the level of the individual and of the social group to demographic processes, movement, social organization and disease dynamics. 3. The probability of an individual being an incident case was greater in groups where TB was already present, although this was less influential in groups that were subject to some instability in numbers. Both individuals and groups were more likely to be incident cases where the social group was diminishing in size, although no relationship was observed with group size itself. This suggests that the process of group size reduction rather than group size per se has most influence on disease dynamics. The likelihood that either an individual or a group was an incident case was positively correlated with both individual and group-level movement. When the proportion of females in a social group was high, the positive association between movement and incidence was found to be more pronounced and there was a significantly higher probability of incident cases among males. 4. These relationships highlight the importance of social structure in driving TB transmission dynamics in this stable, high-density badger population. The results support the idea that a stable social structure mitigates against new incident cases of disease, and are consistent with the contention that badger culling may create the social circumstances for enhanced transmission of TB.

Preliminary comparison of four anaesthetic techniques in badgers (Meles meles)

OBJECTIVE

To investigate the use of four ketamine-based anaesthetic combinations in wild badgers.

STUDY DESIGN

Prospective, randomized, clinical trial.

ANIMALS

Twenty-four adult badgers.

MATERIALS AND METHODS

Animals were divided into four groups of six and were anaesthetized using either intramuscular (IM) ketamine alone (20 mg kg(-1)), ketamine (15 mg kg(-1) IM) and midazolam (0.4 mg kg(-1) IM), ketamine (10 mg kg(-1) IM) and midazolam (1 mg kg(-1) IM) or ketamine (5 mg kg(-1) IM) and medetomidine (80 microg kg(-1) IM) antagonized with atipamezole (0.8 mg kg(-1); IM). Features of each technique, i.e. quality of induction, maintenance and recovery, and the need for additional doses, were assessed using a simple descriptive scale. Physiological variables, i.e. rectal temperature, respiratory rate, heart rate and blood pressure, were also recorded.

RESULTS

Combinations of ketamine and midazolam did not produce adequate anaesthesia. The combination of medetomidine and ketamine had few advantages over ketamine alone.

CONCLUSIONS AND CLINICAL RELEVANCE

These data will contribute to a wider study attempting to refine anaesthetic techniques in badgers.

Mating system of the Eurasian badger, Meles meles, in a high density population

Badgers are facultatively social, forming large groups at high density. Group-living appears to have high reproductive costs for females, and may lead to increased levels of inbreeding. The extent of female competition for reproduction has been estimated from field data, but knowledge of male reproductive success and the extent of extra-group paternity remains limited. Combining field data with genetic data (16 microsatellite loci), we studied the mating system of 10 badger social groups across 14 years in a high-density population. From 923 badgers, including 425 cubs, we were able to assign maternity to 307 cubs, with both parents assigned to 199 cubs (47%) with 80% confidence, and 14% with 95% confidence. Age had a significant effect on the probability of reproduction, seemingly as a result of a deficit of individuals aged two years and greater than eight years attaining parentage. We estimate that approximately 30% of the female population successfully reproduced in any given year, with a similar proportion of the male population gaining paternity across the same area. While it was known there was a cost to female reproduction in high density populations, it appears that males suffer similar, but not greater, costs. Roughly half of assigned paternity was attributed to extra-group males, the majority of which were from neighbouring social groups. Few successful matings occurred between individuals born in the same social group (22%). The high rate of extra-group mating, previously unquantified, may help reduce inbreeding, potentially making philopatry a less costly strategy.

Experimental comparison of ketamine with a combination of ketamine, butorphanol and medetomidine for general anaesthesia of the Eurasian badger (Meles meles L.)

The refinement of anaesthetic regimes is central to improving the welfare of captured wildlife. The Eurasian badger (Meles meles) has been the subject of an intensive long-term ecological and epidemiological study at Woodchester Park, Gloucestershire, England. During routine trapping operations (June 21st, 2000-January 23rd, 2001) an experimental trial was conducted on 89 badgers to compare the physiological effects of anaesthesia using ketamine hydrochloride alone, and in conjunction with medetomidine hydrochloride and butorphanol tartrate. The mixture induced a significantly longer period of anaesthesia, and either substantially reduced or eliminated the adverse effects associated with ketamine anaesthesia (e.g., excessive salivation, bouts of sneezing, rough recoveries, and muscle rigidity). In a sub-sample of badgers given the mixture, anaesthesia was reversed using atipamezole hydrochloride. Under ketamine anaesthesia, heart rates were initially significantly higher and respiration rates were consistently higher, than in badgers given the mixture. In all badgers heart rates declined and respiration rates increased during anaesthesia, but the rate of change was greatest in animals given only ketamine. Overall, the mixture provided a more balanced anaesthesia characterised by muscle relaxation and complete unconsciousness.

Use of cattle farm resources by badgers (Meles meles) and risk of bovine tuberculosis (Mycobacterium bovis) transmission to cattle

Nocturnal observations, radio telemetry and time-lapse camera surveillance were used to investigate visits by badgers (Meles meles L.) to two cattle farms. During 59 half-nights (ca. 295 h) of observation and 17 nights (ca. 154 h) of camera surveillance, 139 separate visits to farm buildings, by at least 26 individually identifiable badgers from two social groups, were recorded. The badgers, which included three individuals infected with bovine tuberculosis (Mycobacterium bovis), used cowsheds, feedsheds, barns, haystacks, slurry pits, cattle troughs and farmyards to exploit a range of food resources, including cattle feed and silage. Cattle feed was contaminated with badger faeces and badgers also came into close contact with cattle. The minimum number of badgers visiting farm buildings per night was negatively correlated with local 24 h rainfall. We conclude that exploitation by badgers of resources provided by cattle farms constitutes a potentially important mechanism for tuberculosis transmission from badgers to cattle.

A DNA vaccine encoding MPB83 from Mycobacterium bovis reduces M. bovis dissemination to the kidneys of mice and is expressed in primary cell cultures of the European badger (Meles meles)

Nucleic acid (DNA) vaccination against tuberculosis in the European badger (Meles meles) is one approach to addressing the escalating problem of bovine tuberculosis in Great Britain. The aim of vaccination is to reduce the burden of tuberculosis within the badger population and the shedding of Mycobacterium bovis to levels that would break the transmission of infection to cattle. To this end, the vaccine would be required to limit the amount of disseminated tuberculosis in the badger, especially dissemination to the kidney from where M. bovis can be shed in the urine. A promising candidate DNA vaccine encoding a 26 kDa major antigen (MPB83) of M. bovis was evaluated in a mouse model of disseminated M. bovis infection. Using the DNA vaccine, protection against infection of the kidney was found to be greater than that achieved with the current live vaccine, Bacille Calmette-Guerin (BCG). Kidney tissue and skeletal muscle from the badger was used to derive primary cell cultures in which to examine the expression of MPB83 following transfection with the DNA vaccine. Kidney cortex gave rise to a monotypic culture of epithelial cells whilst the muscle gave rise to a mixed culture of fibroblasts and myoblasts. During culture the myoblasts differentiated into multinucleated myotubes, verified by immunofluorescent detection of mammalian desmin. Successful expression of MPB83 by transfected epithelial and myotube cells was confirmed by immunofluorescence using a monoclonal antibody specific to the protein. These observations fulfil the early requirements for the development of a DNA vaccine for badger tuberculosis.

A lymphocyte transformation assay for the detection of Mycobacterium bovis infection in the Eurasian badger (Meles meles)

The Eurasian badger (Meles meles) is a significant wildlife reservoir of Mycobacterium bovis in Great Britain. Improved control strategies against the disease in badgers require the development of diagnostic tests and vaccines. Here, we report the development of a comparative lymphocyte transformation assay (LTA) using bovine and avian tuberculin as antigen to detect cell-mediated responses in M. bovis-infected badgers. In a pilot study, the performance of this assay was compared with the existing indirect ELISA assay for the detection of tuberculous badgers. The sensitivity of the Comparative LTA was 87.5% compared with 62.5% for the indirect ELISA whereas the ELISA test gave a greater specificity (100% compared with 84.6% for the comparative LTA). Preliminary evidence suggests that for the comparative LTA, the blood may be stored overnight prior to testing and that this procedure might improve the specificity of the assay without compromising the sensitivity.

Mycobacterium bovis in the European badger (Meles meles): epidemiological findings in tuberculous badgers from a naturally infected population

This study investigates the course of tuberculosis in a naturally infected badger population, its impact on the population and the risk of spread to other species in the light of capture data and post-mortem findings from 47 tuberculous badgers, stratified by age group and sex, accrued since 1975. The findings are compared with those for 260 badgers from the same population in whom no evidence of infection was detected. Detailed estimates of seasonal variations in bodyweight for uninfected male and female cub, yearling and adult badgers are presented and compared to the weights at post-mortem examination of the tuberculous badgers, in whom poor condition and weight loss were the principal presenting signs. Lesions were seen especially in the lungs and associated lymph nodes, and in the kidneys. Organisms were detected intermittently in faeces, urine, sputum and discharging bite wounds. Infected animals could survive for nearly 2 years and produce cubs successfully.

Experimental infection of badgers (Meles meles) with Mycobacterium bovis

The intradermal inoculation of four badgers with small numbers of Mycobacterium bovis resulted in localized lesions with ulceration which slowly healed by 5 months after inoculation. Lesions of generalized tuberculosis were seen in three badgers, one of which died at 17 months post-inoculation and in the remaining two killed 22 months post-inoculation. In the fourth badger lesions were confined to the draining lymph node of the inoculation site but M. bovis was isolated from the liver. Monthly clinical sampling of faeces, urine, tracheal aspirate and inoculation site exudates detected only the excretion of M. bovis from the inoculation site of one badger. There were marked seasonal variations in body weight but significant weight loss was observed during the second year in all four badgers, particularly prior to death. Four badgers inoculated intratracheally with a similar inoculum of M. bovis and another two control badgers showed no evidence of infection with M. bovis.

The immunological consequences of challenge with bovine tubercle bacilli in badgers (Meles meles)

Optimal conditions were determined for performing antibody measurements (ELISA), lymphocyte transformation tests and, to some extent, skin tests in badgers. These parameters, together with the bacteriological and pathological studies reported previously (Pritchard et al. 1987), were used to follow the course of intradermal and intratracheal challenge of badgers with bovine tubercle bacilli. Two challenge doses were used for each route of infection and two animals received each dose. None of the four animals challenged by the intratracheal method showed any evidence of infection, suggesting that adult badgers may have some resistance to challenge by this method. All four animals challenged intradermally developed lesion of tuberculosis. Immunologically the disease passed through three phases. There was an early phase in which lymphocyte transformation to whole BCG steadily and significantly increased, and skin tests to tuberculin became positive but there was little change in antibody levels. This was followed by an intermediate phase of variable skin responses, fluctuating lymphocyte transformation and significant increase in antibody levels. The final phase, which was only seen in two animals with extensive disease, was associated with changing skin reactions and falling lymphocyte responses, together with a sudden increase in antibody levels. This paper presents the first formal evidence of cell-mediated immunity to tuberculosis in the badger, which may delay onset and prolong the survival of challenged animals.

Tuberculosis in East Sussex. III. Comparison of post-mortem and clinical methods for the diagnosis of tuberculosis in badgers

Following epidemiological and ecological studies of a defined badger population in an area of East Sussex, removal of all badgers by cage trapping was attempted. Trapping was incomplete due to the activities of protesters. Forty-seven badgers were caught from the eight social groups. All badgers were examined clinically and samples of faeces, urine and tracheal aspirate were taken, together with swabs from any bite wounds, for bacteriological examinations. Forty-five animals were skin tested using whole killed cells of Mycobacterium bovis strain AN5, bovine PPD Weybridge and new human tuberculin. Skin test results were recorded after 24 and 72 h. All badgers were killed and subjected to a post-mortem and bacteriological examination. M. bovis was detected in 10 (21.3%) badgers at post-mortem and in 2 badgers from clinical samples. Four social groups were infected. Positive skin test results were recorded at 72 h with bovine PPD (2 micrograms and 20 micrograms/ml), strain AN5 (1 mg/ml) and human tuberculin (2 micrograms/ml), but not with human tuberculin at 20 micrograms/ml. Histological sections of the skin test reactions showed the cellular types typical of delayed-type hypersensitivity. The skin test reactions observed were neither sensitive nor specific enough to be of practical value.

Bovine tuberculosis in domestic and wild mammals in an area of Dorset. II. The badger population, its ecology and tuberculosis status

Following a major outbreak of tuberculosis in cattle on a farm in Dorset, badgers were discovered to be infected with Mycobacterium bovis. Two hundred and forty sets were found in the 1200 hectares of the study area. The sets were found predominantly in areas of Portland Sand. A high prevalence of tuberculosis was found in the badger population which was removed and repopulation prevented for 3 years. The removal of the infected badgers led to the resolution of the problem in cattle. Re-colonization of the area has progressed slowly and the cattle have remained free from infection for a period of 5 years.