Sequence and phylogenetic analysis of interleukin (IL)-1beta-encoding genes of five avian species and structural and functional homology among these IL-1beta proteins

Interleukin (IL)-1beta-encoding regions of chicken, duck, goose, turkey and pigeon were cloned and sequenced. Each IL-1beta-encoding region of chicken, duck, goose and turkey is 804 nucleotides long and encodes IL-1beta protein that is 268 amino acids. Pigeon IL-1beta-encoding region is 810 nucleotides long and encodes IL-1beta protein that is 270 amino acids. Two one-nucleotide and one four-nucleotide insertions of pigeon IL-1beta-encoding region sequence were found, resulting in two amino acid insertions in pigeon IL-1beta. Pairwise sequence analysis showed that the sequence identities of IL-1beta-encoding genes ranged from 77% to 99%, which were also found for IL-1beta protein sequence identities, with an average level of both sequence identities of 89%. Phylogenetic analysis indicated that IL-1beta-encoding regions and the encoded proteins of chicken, duck, goose and turkey clustered together and evolved into a distinct phylogenetic lineage from that of pigeon which evolved into a second lineage. The results from the binding reaction of antiserum against each recombinant IL-1beta (r IL-1beta) protein to homologous or heterologous rIL-1beta, the enhancement levels of K60 mRNA expression in rIL-1beta-treated DF-1 cells or the reduction levels of K60 mRNA expression in DF-1 cells treated with rIL-1beta that was preincubated with homologous or heterologous antiserum showed that all five rIL-1beta were functional active and shared significantly structural and functional homology.     

Cloning and expression of bovine and porcine interleukin-2 in baculovirus and analysis of species cross-reactivity

The cDNAs encoding bovine and porcine interleukin-2 (IL-2) have been expressed using the baculovirus Autographa californica nuclear polyhedrosis virus as a vector in insect cells. Insect cells infected with recombinant viruses secreted bovine and porcine IL-2 into the culture medium, with biological activities for maintaining the proliferation of homologous cells. When the activities of these two IL-2 proteins and commercially available human IL-2 were tested on heterologous cells differences were found. Recombinant bovine (rb)IL-2 only supported the growth of bovine lymphocytes and was not active on human, mouse or porcine lymphocytes. Recombinant porcine (rp)IL-2 and recombinant human (rh)IL-2 supported the proliferation of human, bovine, porcine and murine cells. However, the proliferative response of human lymphocytes to rpIL-2 was only 50% of that seen with rhIL-2. Sequence differences at the predicted p55 and p75 contact binding sites may explain this.     

Effects of sustained control of brushtail possums on levels of Mycobacterium bovis infection in cattle and brushtail possum populations from Hohotaka, New Zealand

AIMS: To examine the effect of reducing the abundance of brushtail possums (Trichosurus vulpecula) on the distribution and prevalence of bovine tuberculosis (Mycobacterium bovis, Tb) in possums and the incidence of Tb in domestic cattle on a group of farms in the central North Island, New Zealand. METHODS: The cumulative yearly incidence of Tb infection from 12 cattle herds was estimated from annual tuberculin testing and abattoir inspection data over the period 1983-98. Intensive control of possum populations began for six of the herds in 1988, five herds in 1994 and the remaining herd in 1996. The prevalence and distribution of macroscopic M. bovis infection in possums and an index of possum abundance was estimated during yearly cross-sectional surveys from 1988 to 1998. This enabled formal testing of the link between the abundance of tuberculous possums and the incidence of Tb in cattle. RESULTS: Before possum control, infected possums were clustered in foci on or adjacent to the farms with the highest annual incidence of tuberculosis in cattle, and had an overall prevalence of macroscopic M. bovis infection of 2.3%. The prevalence of disease declined to zero with ongoing possum control, although infected possums continued to be found during the first 5 years of control. Maintaining the possum population at an average of 22.1% of its pre-control density significantly reduced the odds of the cumulative yearly incidence of Tb in cattle by 77% during the first 5 years of possum control and a further 65% in the second 5-year period. Nine of 11 tuberculous possums identified since the start of possum control were found within the areas where infected possums were clustered during the pre-control survey, suggesting that the persistence of infection within these clusters rather than infected immigrants was the source of ongoing disease. Annual estimates of the prevalence of tuberculous possums broadly followed the predictions of Barlow's possum-Tb model for a controlled possum population. CONCLUSION: The results support the hypothesis that tuberculous possums transmit bovine tuberculosis to domestic cattle, and therefore that reducing the abundance of tuberculous possums reduces the incidence of Tb in cattle. If the level of possum culling is sufficient, it appears that M. bovis infection may be eradicated from possum populations. Better information on population density, rate of increase and annual culling rates would have been needed for a truly independent examination of the Barlow possum-Tb model.     

Trends in the incidence of tuberculosis in possums and livestock, associated with differing control intensities applied to possum populations

AIM: To determine the trap-catch index (an estimate of abundance) of brushtail possum (Trichosurus vulpecula) populations infected with bovine tuberculosis (Tb; Mycobacterium bovis) that must be achieved, and the length of time such an index must be maintained, for Tb to be eliminated from possum populations and adjacent livestock. METHODS: Between 1997-1998 and 2000-2001, trap-catch surveys of possum populations naturally infected with Tb and subjected to population-control measures were undertaken at four forest sites and two farmland sites. At the same time, possum carcasses were collected at these sites and their Tb status determined, and all contiguous cattle and deer herds were Tb tested and abattoir slaughter data for these herds were interrogated. RESULTS: Trap-catch surveys indicated that numbers of possums on the farmland sites surveyed were usually very low and well below the control targets set (i.e. a 5% trap catch or approximately 0.5-1 possum/ha) for the study. In contrast, trap-catch surveys undertaken in forest sites indicated possum numbers were more variable, and often recovered rapidly from control operations to exceed control targets within 1-3 years. The annual rate of recovery of possum populations in half of the forest population surveys undertaken exceeded published intrinsic rates of increase for possums. The overall prevalence of Tb in possum populations was < or =1.9% at 5/6 sites, and was 6.5% at the sixth site. Juvenile possums infected with Tb were trapped within but near the edge of control zones and appeared to represent an immigrant source of infection. Mature infected possums survived control operations apparently by having home ranges in uncontrolled patches within control areas. Infection in possums appeared to be eliminated from one study site by the intensive control undertaken, but elimination at other sites appeared less likely. Levels of Tb in livestock on or adjacent to the study sites fell by at least 50% during the study, and cattle in one area tested clear for the first time in 20 years. CONCLUSIONS: Initial control of possums in forest appeared to achieve national control targets set by the Animal Health Board (AHB), despite trap-catch data often providing misleading population estimates. Such targets were often exceeded within 1-3 years. By comparison, possum control on farmland appeared to maintain populations at very low levels, while control on forest margins maintained populations at intermediate levels. Control was least effective in deep forest where human access was most difficult. Intensive population control measures appeared to have led to a reduced incidence of Tb in livestock at 3/4 sites, and elimination of Tb in livestock at one site. This result supports modelling studies that predict the eradication of Tb from possums through ongoing intensive control and may explain the lower success achieved with earlier less-intensive possum control.     

Purification of secretory immunoglobulin A from milk of the brushtail possum (Trichosurus vulpecula)

AIM: To identify and purify secretory immunoglobulin A (sIgA), a key effecter molecule in mucosal immune responses, from milk of the brushtail possum (Trichosurus vulpecula). METHODS: Milk samples were collected from female possums with pouch young, and clarified by centrifugation and precipitation methods. The clarified fraction was purified by gel filtration and affinity chromatography to yield sIgA. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDSPAGE) and immunoblotting techniques were used to assess the purity of the final product, and to identify the heavy (H) chain, light (L) chain and secretory component (SC) of possum sIgA. RESULTS: Immunoblotting, using antibodies raised against cloned possum sIgA SC and H-chain, and a synthetic peptide fragment of the H-chain, confirmed the identity of the purified protein. The N-terminal amino acid sequence of purified possum sIgA showed strong homology to reported sequences of H-chain variable regions of marsupial immunoglobulins. CONCLUSIONS: Milk was shown to be a convenient source of mucosal secretion containing sIgA, and a process involving 2 precipitation and 2 chromatography steps produced purified sIgA. This IgA preparation will prove useful for the generation of sIgA-specific immunological reagents for measurement of immune responses in the development of mucosal-based vaccines for biological control of possums.     

Vaccination of the brushtail possum (Trichosurus vulpecula) against Mycobacterium bovis infection with bacille Calmette-Guérin: the response to multiple doses.

In New Zealand, the brushtail possum (Trichosurus vulpecula) is the principal wildlife vector of bovine tuberculosis. Control of infected possum populations contributes to the control of tuberculosis in domestic livestock. Vaccination is potentially a complementary strategy to population control, but to be cost-effective, administration of the vaccine to possums would need to be from an appropriately designed automatic vaccinator. Possums themselves would activate the vaccinator so that it would deliver an aerosol spray of vaccine. There would be no direct way to prevent possums receiving multiple doses of vaccine. This study examined the effect on protective immunity of repeated vaccination. Captive possums were vaccinated with BCG strain pasteur 1173P2 either 12 times at weekly intervals, twice at 6-weekly intervals, or once. Vaccination was by a combination of intranasal aerosol and conjunctival instillation. Eight weeks after the last dose of vaccine, all possums were challenged intratracheally with Mycobacterium bovis strain 83/6235. Vaccination induced a significant immune response as measured by the lymphocyte proliferation assay (LPA). A significant level of protection, as measured by the response to challenge, developed in all the vaccinated possum groups, but protection was greatest in the group vaccinated 12 times. It was concluded that protection would be enhanced if vaccinations were repeated at short intervals (weekly), but no benefit or detriment resulted from revaccination after longer intervals (1-2 months).     

Contact patterns as a risk factor for bovine tuberculosis infection in a free-living adult brushtail possum Trichosurus vulpecula population

The aim of this study was to identify risk factors for bovine tuberculosis (TB) in a free-roaming, capture-mark-recapture monitored possum Trichosurus vulpecula population in a 22-ha study site at Castlepoint, New Zealand from 1 April 1989 to 31 March 1994. A matched case-control design was used to evaluate the influence of sex, habitat and contact opportunities on TB risk. Cases comprised possums identified as TB-positive throughout the study period. Controls were selected from the group of possums that were captured and showed no clinical signs of TB throughout the study period. Measures derived from a social network analysis of possum capture locations such as degree, clustering coefficient (CC) and betweenness were used to represent potential contact opportunities among possums. Network analysis measures recorded for individual possums in the 12-month period before a diagnosis of TB were evaluated in a conditional logistic regression model. We found no evidence of an association between case status and the total number of possums with which there was potential contact (degree) (P=0.5). The odds of cases being exposed to unit increases in the number of TB-positive contacts was 2.50 (95% CI 1.24-5.05; P<0.01) times that of controls. This effect was conditional on the total number of potential contacts made, with a negative interaction with increasing degree. These findings indicate that potential contact with TB-positive possums increases the odds of disease whereas potential contact with large numbers of possums does not. This suggests that multiple contacts with TB-positive possum(s) are necessary for transmission of TB and this is more likely to occur in networks that are smaller. We challenge the hypothesis that contact with large numbers of individuals increases the probability of becoming TB infected and argue that individual contact behaviour is a determinant of the creation of TB foci within free-living possum populations.     

Interactions between beef cattle and simulated tuberculous possums on pasture

Brushtail possums (Trichosurus vulpecula) were sedated with ketamine and placed within a fenced observation area with 17 Hereford cross steers. The behaviour of the sedated possums simulated that of terminally ill possums. Behavioural analysis was carried out during eight observation periods in which sedated possums were successfully released and interactions occurred. Cattle were attracted from over 50 m away by the movements of the possums, and for 34% of observation time cattle investigated the possums. Inactive animals engendered far less interest, and cattle investigated them for 3% of observation time. An average of seven to eight cattle came in physical contact with the possum in each of the observation periods. Cattle actively investigated the possum while following it as it moved, commonly close enough to be within aerosol transmission distance, and some sniffed the possum, touched it with their noses, and in many cases licked it extensively. All of these activities would expose the cattle to high risk of receiving an infective dose of Mycobacterium bovis, especially via the respiratory route. The type and duration of contact between individual steers and the possum varied between animals and observation period. The cattle exposed themselves to greater risk, overall, during the first week of observations, and there was evidence of habituation with increased contact. Although all 17 steers came within 5 metres of the possum at some point during the observation periods, some individual cattle behaved in ways which would put them at greater risk of contracting tuberculosis than did others. Cattle showed little interest in possum carcasses placed on pasture. These were unlikely to be a significant source of infection for cattle, although they could be for scavenger species.     

Behavioural studies on the potential for direct transmission of tuberculosis from feral ferrets (Mustela furo) and possums (Trichosurus vulpecula) to farmed livestock

Studies were conducted to evaluate the response of cattle and deer to ferrets which were sedated so they behaved like terminally tuberculous animals, and to compare this with the response of cattle, deer and sheep to sedated possums. Six groups of deer and two groups of cattle were exposed to a sedated ferret and to a sedated possum. Both livestock species showed interest in the possum by sniffing and licking it, but they only briefly touched the ferret and no licking or extended investigation was observed. The proportion of available time spent in physical contact with the possum by cattle was 7.7 times as high as for the ferret, and for the deer was 5.7 times as high. The behavioural response of three groups of sheep to a sedated possum was investigated, and sheep showed limited interest beyond viewing the possum from a distance. The amount of time spent by sheep investigating the possum was very low and the intensity of exploration was also low. For possums, at least one deer was within 1.5 m (an estimate of the distance that tuberculosis can be transmitted by aerosol) for 50.9% of observation time, and in physical contact with the possum for 9.5% of time. The figures for cattle were 69.3% and 17.3%, while those for sheep were 6.9% and 0.3%. In interactions with ferrets, the equivalent figures were 29.8% within 1.5 m and 2.2% in physical contact for cattle, and 20.8% and 1.1% for deer. Tuberculous possums commonly and tuberculous ferrets less commonly have lung lesions and/or discharging sinuses, and may excrete Mycobacterium bovis intermittently or continuously in aerosols or discharges. The exploratory behaviour of deer and cattle in this study would provide opportunities for them to become infected with M. bovis if they had contact with infectious possums, and less probably with ferrets. The response of sheep to possums suggests that they would be much less likely to contract the disease.     

Toxoplasmosis as a cause of ovine perinatal mortality

Aims. To determine temporal and spatial patterns of bovine tuberculosis (Tb) in a population of brushtail possums (Trichosurus vulpeculu) free from commercial and recreational hunting and living contiguously with livestock, and to relate these patterns to measures of possum health and density.

Methods. Possums were trapped on 11 lines located on a forest-rough grazing margin in the Ahaura Valley in Westland in 1979-80 and each August from 1992 to 1996, and were examined post mortem for gross lesions indicative of Tb. Infection levels in possums were compared with Th test data from cattle grazing in the same area.

Results. Tuberculosis was identified from the trapped sample of possums in 1980. Trapping of further possums on the same trap lines confirmed the presence of the disease each year from 1992 to 1996, and suggested a clustering of infection in time and space. The prevalence of Th in possums declined with increasing possum population size and well being, and decreasing age. The prevalence of Tb in possums was highest in 1980 and 1992, and appeared to roughly coincide with similar upsurges in Tb in nearby cattle.

Conclusions. Our results suggest that the exceptional levels of Tb recorded in possums in 1992 had a direct effect on possum numbers, and gave rise to very low trap catches in 1993-94. They also suggest thatTb can persist for several years in possum populations existing well below the 5% trap catch targeted by regipnal councils forTb possum control.     

Temporal patterns in bovine tuberculosis in a brushtail possum population contiguous with infected cattle in the Ahaura Valley, Westland

AIMS: To determine temporal and spatial patterns of bovine tuberculosis (Tb) in a population of brushtail possums (Trichosurus vulpecula) free from commercial and recreational hunting and living contiguously with livestock, and to relate these patterns to measures of possum health and density. METHODS: Possums were trapped on 11 lines located on a forest-rough grazing margin in the Ahaura Valley in Westland in 1979-80 and each August from 1992 to 1996, and were examined post mortem for gross lesions indicative of Tb. Infection levels in possums were compared with Th test data from cattle grazing in the same area. RESULTS: Tuberculosis was identified from the trapped sample of possums in 1980. Trapping of further possums on the same trap lines confirmed the presence of the disease each year from 1992 to 1996, and suggested a clustering of infection in time and space. The prevalence of Tb in possums declined with increasing possum population size and well being, and decreasing age. The prevalence of Tb in possums was highest in 1980 and 1992, and appeared to roughly coincide with similar upsurges in Tb in nearby cattle. CONCLUSIONS: Our results suggest that the exceptional levels of Tb recorded in possums in 1992 had a direct effect on possum numbers, and gave rise to very low trap catches in 1993-94. They also suggest that Tb can persist for several years in possum populations existing well below the 5% trap catch targeted by regional councils for Tb possum control.     

A behaviour study on the potential for direct transmission of tuberculosis from possums (Trichosurus vulpecula) to alpacas (Lama pacos), and the converse from alpacas to possums

AIMS: To evaluate the potential for the direct transmission of tuberculosis from possums to alpacas, and vice versa. METHODS: A field study was conducted on an alpaca farm in Northland, New Zealand on 7 January 1999. Observations were recorded on the interaction of one group of male alpacas with a simulated dead possum, one male and one female alpaca group with a simulated terminally tuberculous possum, and one group of male alpacas with a normal possum in an enclosure from which the animals could not escape. The possum was sedated with ketamine as hydrochloride to simulate death (inactive; no movement), and terminal illness (active, inco-ordinated movement around the paddock). The observations were based on the focal animal sampling technique, they were un-replicated, and recorded visually and manually with intermittent still photography. RESULTS: Both male and female alpacas showed strongly inquisitive interaction with the possum. They clustered around the possum (focal animal) very soon after it was observed by the first member of the group. The interest of the majority of both sex groups remained high for the observation periods of approximately 30 minutes, and most individuals remained within 5 metres of the possum for that time. Approximately 50% of the alpacas were within possible aerosol transmission distance of 2 metres from the sedated, erratically mobile possum with their heads towards it for approximately 50% of the two observation periods. Aggressive behaviour was recorded for a young male with stamping on the moving possum. Similar, but more vigorous and prolonged stamping behaviour was recorded for a female with a young (<1 week) offspring (cria). The stamping behaviour was accompanied by very close nose to nose contact of the alpaca and possum. At one point the female threw the possum approximately 1.5 metres in the air with her teeth. The group of male alpacas placed in an enclosure with an unsedated normal possum generally moved away from the possum during its rapid active attempts to escape. When it became inactive their approaches were cautious and only once elicited a defence reaction from the possum, from which they recoiled. One male made one attempt to stamp on the active possum. Soon after the possum became inactive in a small loose hay pile, the alpacas lost interest in it. CONCLUSIONS: The alpaca / possum behavioural interactions show there is potential for direct aerosol transmission of tuberculosis from possums to alpacas, but probably not from alpacas to possums.     

Interleukin-12 (IL-12) ameliorates the effects of porcine respiratory and reproductive syndrome virus (PRRSV) infection

Porcine respiratory and reproductive syndrome virus (PRRSV) disease, one of the most economically significant viral diseases in the swine industry, is characterized by miscarriages, premature farrowing, stillborn pigs, and respiratory disease associated with death and chronic poor performance of nursing and weaned pigs. Interleukin-12 (IL-12) is a key component in driving the development of cell-mediated immunity as well as stimulating interferon-gamma (IFN-gamma) production from T cells and natural killer cells. Although some studies have investigated the use of IL-12 as a vaccine adjuvant in swine, little is known about its effectiveness as a treatment against viral diseases in swine. The present study investigated whether recombinant porcine IL-12 (rpIL-12) enhances the immune response and thereby diminishes the effects of PRRSV infection in young pigs. Interestingly, in vitro experiments demonstrated that rpIL-12 is capable of inducing swine pulmonary alveolar macrophages (PAMs), the target cells of PRRSV, to produce IFN-gamma in a dose and time dependent manner. In addition, in vitro studies also revealed that rpIL-12 treatment was capable of significantly reducing PRRSV viral titers in PAMs. In vivo administration of rpIL-12 significantly decreased PRRSV titers in the lungs and blood of infected animals. Furthermore, treatment with rpIL-12 prevented significant growth retardation in PRRSV-infected animals. Finally, in response to viral antigen recall challenge, PAMs isolated from rpIL-12-treated/PRRSV-infected animals produced greater amounts of IFN-gamma and lesser amounts of interleukin-10 than PAMs isolated from non-rpIL-12-treated/PRRSV-infected animals. Taken together our data indicate that treatment with rpIL-12 may provide an effective approach to control or ameliorate PRRSV-induced disease in swine.     

Purification of secretory immunoglobulin A from milk of the brushtail possum (Trichosurus vulpecula)

AIM: To identify and purify secretory immunoglobulin A (sIgA), a key effecter molecule in mucosal immune responses, from milk of the brushtail possum (Trichosurus vulpecula).

METHODS: Milk samples were collected from female possums with pouch young, and clarified by centrifugation and precipitation methods. The clarified fraction was purified by gel filtration and affinity chromatography to yield sIgA. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting techniques were used to assess the purity of the final product, and to identify the heavy (H) chain, light (L) chain and secretory component (SC) of possum sIgA.

RESULTS: Immunoblotting, using antibodies raised against cloned possum sIgA SC and H-chain, and a synthetic peptide fragment of the H-chain, confirmed the identity of the purified protein. The N-terminal amino acid sequence of purified possum sIgA showed strong homology to reported sequences of H-chain variable regions of marsupial immunoglobulins.

CONCLUSIONS: Milk was shown to be a convenient source of mucosal secretion containing sIgA, and a process involving 2 precipitation and 2 chromatography steps produced purified sIgA. This IgA preparation will prove useful for the generation of sIgA-specific immunological reagents for measurement of immune responses in the development of mucosal-based vaccines for biological control of possums.     

Resolution of Mycobacterium bovis infection in wild brushtail possums (Trichosurus vulpecula)

The brushtail possum (Trichosurus vulpecula) is the principal wildlife reservoir of Mycobacterium bovis in New Zealand (Morris and Pfeiffer 1995). Tuberculosis in possums is a progressive, fatal infection. The complete resolution of infection in possums has not been reported. The purpose of this communication is to present two cases of complete and spontaneous resolution of tuberculosis in wild, naturally infected possums. During an 11-year (1989-2000) longitudinal study of a possum population at Castlepoint in the Wairarapa, 90 bacteriologically-confirmed cases of M. bovis infection were observed, and 88 of the tuberculous possums were either found dead or were presumed to have died when they ceased to be trapped. As the home range of adult possums is stable (Efford et al 2000) it was assumed that if an adult possum could no longer be trapped, it had died. In many cases, the declining physical condition of a tuberculous possum prior to its disappearance supported the assumption. However, two cases survived and were euthanised, one 15 months and the other 30 months after they first showed clinical signs of infection. When examined post mortem, neither showed evidence of M. bovis infection. The case histories are described and the significance of the observations discussed.     

A neurological syndrome in a free-living population of possums (Trichosurus vulpecula)

AIMS: To determine the clinical and pathological features of a neurological disease syndrome in a free-living possum population in New Zealand and to compare this syndrome with wobbly possum disease. METHODS: An outbreak of a neurological disease in possums in the Rotorua district was investigated in 1994. A variety of tissues was collected and investigated microbiologically and histopathologically. Tissues stored from clinically affected possums were homogenised, clarified and inoculated into healthy possums by the intra-peritoneal route. The clinical signs and histopathological lesions in naturally-infected and in experimentally-inoculated possums were assessed and compared with those of possums affected with wobbly possum disease. RESULTS: Histopathological investigation of three of the naturally-affected possums revealed non-suppurative encephalitis with perivascular cuffing, diffuse non-suppurative meningitis and focal non-suppurative myocarditis. These lesions were suggestive of a viral infection. No pathogenic bacteria were recovered and no viruses were isolated in tissue culture. A neurological disease, indistinguishable from wobbly possum disease, was reproduced in five out of the eight experimentally inoculated possums. In two experimental cases the clinical signs were very mild and, in most cases of the natural and experimental disease, histopathological lesions in the central nervous system were mild in comparison with wobbly possum disease. Possums which did not develop clinical signs of neurological disease or have lesions in the central nervous system did have infiltrations of mononuclear inflammatory cells in the liver and kidney. CONCLUSIONS: This neurological disease, reported for the first time in a free-living population, closely resembles and may be the same as wobbly possum disease. The milder nature of this disease could suggest there may be more than one strain of the aetiological agent.     

A behaviour study on the potential for direct transmission of tuberculosis from possums (Trichosura vulpecula) to alpacas (Lama pacos), and the converse from alpacas to possums

Aims. To evaluate the potential for the direct transmission of tuberculosis from possums to alpacas, and vice versa.

Methods. A field study was conducted on an alpaca farm in Northland, New Zealand on 7 January 1999. Observations were recorded on the interaction of one group of male alpacas with a simulated dead possum, one male and one female alpaca group with a simulated terminally tuberculous possum, and one group of male alpacas with a normal possum in an enclosure from which the animals could not escape. The possum was sedated with ketamine as hydrochloride to simulate death (inactive; no movement), and terminal illness (active, into-ordinated movement around the paddock). The observations were based on the focal animal sampling technique, they were un-replicated, and recorded visually and manually with intermittent still photography.

Results. Both male and female alpacas showed strongly inquisitive interaction with the possum. They clustered around the possum (focal animal) very soon after it was observed by the first member of the group. The interest of the majority of both sex groups remained high for the observation periods of approximately 30 minutes, and most individuals remained within 5 metres of the possum for that time. Approximately 50% of the alpacas were within possible aerosol transmission distance of 2 metres from the sedated, erratically mobile possum with their heads towards it for approximately 50% of the two observation periods. Aggressive behaviour was recorded for a young male with stamping on the moving possum. Similar, but more vigorous and prolonged stamping behaviour was recorded for a female with a young (<1 week) offspring (cria).The stamping behaviour was accompanied by very close nose to nose contact of the alpaca and possum. At one point the female threw the possum approximately 1.5 metres in the air with her teeth. The group of male alpacas placed in an enclosure with an unsedated normal possum generally moved away from the possum during its rapid active attempts to escape. When it became inactive their approaches were cautious and only once elicited a defence reaction from the possum, from which they recoiled. One male made one attempt to stamp on the active possum. Soon after the possum became inactive in a small loose hay pile, the alpacas lost interest in it.

Conclusions. The alpaca / possum behavioural interactions show there is potential for direct aerosol transmission of tuberculosis from possums to alpacas, but probably not from alpacas to possums.     

Exercise-induced alterations in pro-inflammatory cytokines and prostaglandin F2alpha in horses

Using an established standardized exercise test on a high-speed treadmill, thirteen Thoroughbred racehorses were exercised to fatigue (failure); blood samples were obtained before exercise, at failure, and at 2, 6, 24, 48, and 72 h after exercise. The exercise test induced a systemic inflammatory response characterized by a mild transient endotoxemia, leukocytosis, increased leukocyte expression of mRNA for tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, and IL-6, and increased circulating concentrations of TNF-alpha and prostaglandin F2 alpha (PGF 2 alpha), with the most pronounced changes being evident at failure and 2h after exercise. Expression of mRNA for IL-6, TNF-alpha, and IL-1 beta was increased by 120-fold, three-fold, and four-fold, respectively, when compared to pre-exercise values. Plasma concentrations of 6-keto-PGF1alpha and PGE2 did not change in response to the exercise test. Collectively, these findings indicate that brief, strenuous exercise induces endotoxemia and a systemic pro-inflammatory response in horses that persists for at least 2h.