Increased food availability raises eviction rate in a cooperative breeding mammal.

In group-living mammals, the eviction of subordinate females from breeding groups by dominants may serve to reduce feeding competition or to reduce breeding competition. Here, we combined both correlational and experimental approaches to investigate whether increases in food intake by dominant females reduces their tendency to evict subordinate females in wild meerkats (Suricata suricatta). We used 20 years of long-term data to examine the association between foraging success and eviction rate, and provisioned dominant females during the second half of their pregnancy, when they most commonly evict subordinates. We show that rather than reducing the tendency for dominants to evict subordinates, foraging success of dominant females is positively associated with the probability that pregnant dominant females will evict subordinate females and that experimental feeding increased their rates of eviction. Our results suggest that it is unlikely that the eviction of subordinate females serves to reduce feeding competition and that its principal function may be to reduce reproductive competition. The increase in eviction rates following experimental feeding also suggests that rather than feeding competition, energetic constraints may normally constrain eviction rates.

Social capital and physiological stress levels in free-ranging adult female rhesus macaques.

Social animals with greater access to social support, i.e. higher levels of social capital, may be able to cope better with the challenges they face in their day-to-day lives, and this may be reflected in lower physiological stress levels. Here, we examine the relationship between social capital and fecal glucocorticoid (GC) levels in pregnant free-ranging adult female rhesus macaques. In addition to social capital measures based on direct connections between social partners, which have been examined previously, we use social network analysis to generate measures of social capital based on indirect connections (i.e. connections between pairs of individuals which result from their mutual direct connection to a third party). We consider social capital based on three different types of affiliative association: grooming, the exchange of affiliative vocalizations and proximity. After controlling for variables known to affect GC output in primates (e.g. month of pregnancy), GC levels of females were significantly predicted by a social network measure of indirect connectedness in the proximity network, proximity reach, in interaction with dominance rank. High ranking females had significantly lower GC levels in months in which they had low levels of proximity reach (i.e. in months in which their proximity networks were smaller and therefore more focused). The results of our study add to a growing body of evidence which suggests that social capital may be an important means by which gregarious animals cope with day-to-day challenges. Our study also joins a small body of recent research which has demonstrated that indirect connections may be important factors in the lives of social animals.

Comparative study of serological methods for the detection of antibodies to porcine reproductive and respiratory syndrome virus.

A comparison was made of serological diagnostic methods used for the detection of antibodies against porcine reproductive and respiratory syndrome (PRRS) virus. In the "phase I" PRRS test panel comparison, a panel of sera collected from 135 pigs of various ages, from North American herds with and without PRRS histories, were sent to 4 different laboratories and tested by an indirect immunofluorescent assay (IFA), an immunoperoxidase monolayer assay (IPMA) and an indirect enzyme-linked immunosorbent assay (iELISA). In the "phase II" PRRS test panel comparison, a panel of 382 sera collected from pigs of various ages, PRRS histories, and from various locations in North America and France, were divided into 2 panels (A & B) and sent to 3 Canadian laboratories and tested by the IFA and iELISA. In the phase I comparison, agreement between the IFA of laboratory 4 and the iELISA and IPMA of laboratory 3 was excellent (kappa values of 95% and 98%, respectively). This contrasted with the poor agreement between these laboratories and the IFA results of laboratories 1 and 2 in the phase I trial. In the phase II comparison, the results demonstrated good agreement between various tests both within and between laboratories. The overall performance of the iELISA was superior in the combination of sensitivity (96.1%) and specificity (100%) relative to the reference classification of the serum samples and repeatability (kappa value 98%). The iELISA is technically superior to IFA and IPMA, time efficient, cost effective and suitable for testing of a large number of samples over a short period of time. Thus, the iELISA may be a better alternative to IFA or IPMA for routine detection of PRRS viral antibodies in swine sera.

Evaluation of the persistence of porcine reproductive and respiratory syndrome virus in pig carcases.

The presence of porcine reproductive and respiratory syndrome (PRRS) virus in pig meat was assessed in samples collected from experimentally infected pigs and from the carcases of pigs from infected herds at an abattoir. In the experimental study, pigs approximately six months old were inoculated with two isolates of PRRS virus and tissue samples were collected seven and 14 days after inoculation. At seven days, PRRS virus was recovered from lungs, tonsils, lymph nodes and muscle tissues, and viral antigens were detected by immunogold silver staining (IGSS) in formalin-fixed lungs, tonsils and scattered cells in muscle tissues. Neither PRRS virus nor antigens were detected in muscle tissue samples collected 14 days after inoculation. In the abattoir pigs, attempts were made to isolate PRRS virus from a total of 44 samples of muscle tissue, collected as pools, from the carcases of 44 pigs originating from seropositive herds. No PRRS virus could be isolated on porcine alveolar macrophages from these 44 muscle tissue samples and no PRRS virus antigens could be detected by IGSS in the formalin-fixed tissue samples. Although the results of experimental infections indicated that PRRS virus may be recovered from muscle tissues early after infection with the virus, the presence of PRRS virus in muscle tissues from carcases of slaughter pigs previously exposed to the PRRS virus could not be demonstrated.

Isolation and experimental oral transmission in pigs of a porcine reproductive and respiratory syndrome virus isolate.

A virus inducing a cytopathic effect on porcine alveolar macrophages was isolated from the lungs of a pig with respiratory problems and lesions of proliferative and necrotizing pneumonia. The isolate was found to react with porcine reproductive and respiratory syndrome virus (PRRSV) monoclonal antibodies by indirect immunofluorescence and was designated LHVA-93-3. The virus could also be propagated on the MARC-145 cell line. The LHVA-93-3 macrophage-passaged isolate was inoculated orally or intranasally in four-week-old specific pathogen-free pigs. Histologically, focal to multifocal lesions of proliferative, necrotizing and interstitial pneumonia could be observed in the lungs of pigs inoculated orally or intranasally, 6 and 10 days post-inoculation. Virus could be reisolated from essentially the same tissues including serum following both routes of infection. The distribution of PRRSV antigens in fixed tissues as determined by immunogold silver staining (IGSS) was similar in orally or intranasally inoculated pigs. The results of this experimental transmission study indicate that pigs may become infected by PRRSV following oral as well as intranasal exposure.

In vitro fertilization and culture of ova from heifers infected with bovine herpesvirus-1 (BHV-1).

Oocytes collected from heifers infected experimentally with bovine herpesvirus-1 (BHV-1, 10(8) TCID(50)/ml) and from dexamethasone-treated (stressed) BHV-1 seropositive animals were matured, fertilized and co-cultured in vitro for 7 d prior to being tested for the presence of the virus. Nineteen of the 21 infected donors yielded embryos and follicular fluids that were BHV-1 positive. Oviductal cells (17 21 ) and uterine fluids (14 21 ) were also positive. Titers for the positive samples ranged 10(1.6)-10(9.6) TCID(50)/ml. The cleavage rate and the proportion of blastocysts that developed from oocytes of BHV-1 infected animals were 26% (n=361) and 6% compared with 56% (n=112) and 26% for uninfected control donors (P<0.05). In contrast, embryos produced from dexamethasone-treated animals tested negative for BHV-1 and yielded 11% blastocysts as compared with 25% for the control group. The results indicate that transferable-stage embryos can be produced by IVF from infected BHV-1 animals and that such embryos are associated with the virus, and might have potential for disease transmission.

Immunohistochemical detection of porcine reproductive and respiratory syndrome virus using colloidal gold.

Two cytopathic agents were isolated on porcine alveolar macrophages following inoculation with homogenates of lung tissues from pigs showing respiratory problems. These isolates were identified as porcine reproductive and respiratory syndrome (PRRS) virus isolates by indirect immunofluorescence using a PRRS virus (PRRSV) specific monoclonal antibody (MAb) and were designated as LHVA-92-1 and LHVA-92-2. Immunogold electron microscopy using a porcine PRRS positive serum pool and protein A-gold resulted in an intense labelling of aggregates of viral particles. Dark specific cytoplasmic staining of porcine alveolar macrophages infected with both virus isolates could be observed by immunogold silver staining (IGSS) using the specific MAb. This method proved effective in detecting PRRSV antigens in several ethanol-fixed tissues of piglets intranasally inoculated with the supernatants of macrophages infected with each isolate. Immunogold silver staining was also successfully used for the detection of PRRSV antigens on sections of formalin-fixed paraffin-embedded lung tissues and on frozen sections of lungs. The present results indicate that colloidal gold may be useful for the identification and immunohistochemical detection of PRRSV in tissues.

Porcine respiratory coronavirus in Quebec: Serological studies using a competitive inhibition enzyme-linked immunosorbent assay.

Porcine respiratory coronavirus (PRCV) was identified for the first time in Quebec, using a blocking enzyme-linked immunosorbent assay (ELISA). Unlike the virus neutralization test (VNT), this ELISA was able to distinguish transmissible gastroenteritis virus (TGEV) from PRCV. Among the 15 seropositive fattening herds from group A, sera containing PRCV antibodies represented 74.8%, whereas those with TGEV antibodies represented only 7.2%. In group B, which consisted of 15 sow herds, nine herds expressed only PRCV-specific antibodies while the other herds had animals positive for TGEV-specific antibodies.

Inactivation of bovine herpesvirus-1 and bovine viral diarrhea virus in association with preimplantation bovine embryos using photosensitive agents.

Hematoporphyrin (HP), hematoporphyrin derivative (HPD), and thiopyronine (TP) are photosensitive agents (PSA) that have a germicidal effect when they are activated by light: helium neon laser (He/Ne) light (HP, HPD), white light (HP, HPD), and yellow-green light (TP). Experiments were conducted with appropriate controls to determine the effect of photosensitive agents a) for inactivating bovine herpesvirus-1 (BHV-1; titre 10(6) TCID50/ml) and bovine viral diarrhea virus (BVDV; titre 10(6) TCID50/ml); b) for disinfecting Day-7, zona pellucida-intact (ZP-I) bovine embryos that had been exposed to BHV-1 (titre 10(6) TCID50/ml) or BVDV (titre 10(6) TCID50/ml); and c) on the in vitro development of embryos. Exposure to HP, HPD and TP followed by light irradiation inactivated BHV-1 and BVDV. Embryos exposed to BHV-I were disinfected by HP or HPD (5 microg/ml) in combination with He Ne light, or by HP or HPD (10 microg/ml) in combination with white light. Embryos exposed to BVDV were disinfected by HPD (5 and 10 microg/ml) followed by He Ne or white light irradiation. Exposure of embryos to light alone or to light and HP or HPD had no detrimental effect on their in vitro development; however, exposure of embryos to TP (5 microg/ml) followed by irradiation caused embryonic degeneration. Exposure of embryos to 5 microg of HPD followed by He Ne light, or 10 microg/ml of HP or HPD, followed by white light, is simple methods of disinfecting them of BHV-I and BVDV.

A survey of cattle for antibodies against bluetongue and epizootic hemorrhagic disease of deer viruses in British Columbia and southwestern Alberta in 1987.

In 1987 a serological survey of cattle for antibodies (Ab) to bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) was undertaken in British Columbia and southwestern Alberta after infection with the viruses was diagnosed in wild and domestic ruminants in the Okanagan Valley. Of 4610 cattle tested, five had Ab only to BTV, 125 had antibodies only to EHDV and 16 had Ab to both viruses. The Ab were identified as specific for BTV type 11 (BT-11) or EHDV type 2 (EHDV-2). All but one of the seropositive cattle originated in the Okanagan Valley of British Columbia. The remaining one seropositive animal which had Ab to EHDV-2 was pastured with a bull purchased from the Okanagan Valley.

Dot immunoperoxidase assay using monoclonal antibody for detection of bluetongue virus antigens.

A rapid, simple dot immunoperoxidase assay (DIPA) is described for visual detection and identification of bluetongue virus (BTV) antigens in samples of infected cell culture fluid. The assay was performed using nitrocellulose (NC) paper and 'dipsticks'. Dots of samples were adsorbed to the NC surface and the remaining non-specific binding sites were blocked with skim milk solution. BTV was detected with either of two murine monoclonal antibodies (4H4, 5G12) to the major group specific antigens of BTV, and the complex was reacted with a peroxidase conjugated anti-mouse immunoglobulin G (heavy- and light-chain specific). Positive reactions were easily visualized as brown spots after enzyme degradation of substrate containing H2O2 and diaminobenzidine (DAB). The DIPA was specific in detecting BTV in samples of cell culture fluid from baby hamster kidney (BHK-21) cells infected with U.S.A. isolates of the five BTV serotypes (2, 10, 11, 13 and 17) known to exist in the U.S.A., and South African isolates of 17 BTV serotypes (1-12, 14-16, 18 and 20), but not with two North American isolates of epizootic hemorrhagic disease of deer virus (EHDV) representing serotypes 1 and 2. Attempts to detect BTV directly in infected sheep blood cells and chick embryo tissue suspensions by DIPA were unsuccessful. Of 55 cell culture fluid samples examined from BHK-21 or Vero cell monolayers inoculated with 55 clinical specimens, propagated initially in embryonating chicken egg (ECE) 11 proved positive and 44 were negative by DIPA. The results were in complete agreement with the conventional ECE and tissue culture isolation systems. The DIPA appears to have potential application, especially as a 'dipstick' kit, for rapid and inexpensive laboratory diagnosis of bluetongue virus infection.

Comparative evaluation of the fluorescent antibody test and microtiter immunoperoxidase assay for detection of bovine viral diarrhea virus from bull semen.

An indirect immunoperoxidase staining technique (IP) is described for the detection of bovine viral diarrhea virus (BVDV) in bovine semen. The performance of the IP was compared to the reference immunofluorescent staining test in its ability to detect BVDV in 23 coded field semen samples. The IP assay which can be applied with ease to a large number of samples and does not require expensive fluorescence microscope equipment, appears to be an alternative method for BVDV detection. The IP assay can be strongly recommended for certification of BVDV-free bovine semen for artificial insemination and trading purposes and for laboratories which are not equipped for performing the immunofluorescent test.

Feeding and emigration of the ant Tapinoma erraticum (Formicidae Dolichoderinae). Experimental analysis of the use of space.

Visits to feeding sites and potential nesting sites by several colonies of Tapinoma erraticum was studied in the laboratory. During the feeding phase ant use of space was significantly asymmetrical (different visit frequencies to identical sites) and reflects environmental structuring. Such asymmetrical patterns of space use may have influenced subsequent orientation of nest search and nest site selection after experimental disturbance. When the colony was disturbed, i.e when the water source and the opaque nest cover were removed activity remained mainly diurnal. There was relative increase in frequency of visits to the subsequently chosen nesting site as compared with visits to feeding sites. Selected nests could be in a zone visited frequently before disturbance, for example close to a feeding source, but other parameters must be considered to account for colony choice. The question of a collective decision making is discussed.