What can zookeepers tell us about interacting with big cats in captivity?

Despite the potential dangers involved, interactions between zookeepers and captive big cats are increasing. Research with other animals, particularly nonhuman primates, suggests that closer interactions can be beneficial not only for the animals and their keepers, but also for zoo visitors. This study sought to determine whether the same benefits may apply to keeper-big cat interactions. An online questionnaire was completed by 86 keepers worldwide, assessing which types of handling (hands-on, protected, hands-off) they practice with their big cats, whether they practice training, and what their opinions of these methods are (through a series of rating scales and open-ended questions). Protected contact was the most frequently used handling method among this sample, particularly with lions, tigers, and cheetahs, and training was practiced by the majority of participants with all big cat species. Participants perceived protected contact as the most beneficial handling practice for big cats, keepers, and visitors, noting how it can allow a close bond between keeper and cat, as well as its educational value for zoo visitors. Contrastingly, concerns were raised about the use of hands-on approaches, particularly with regard to the safety of all parties involved and the potential for wrong messages to be sent to visitors. Further, training was reported to be more beneficial for each group than any handling practice, yielding similar potential benefits as protected contact. Consistent with existing information with other species, these findings will be useful in directing objective research examining the use of different handling and training methods with big cats.

Hypertrophic osteopathy associated with pulmonary Eikenella corrodens infection in a dog.

CASE DESCRIPTION: A 4-year-old English Pointer was examined because of chronic, progressive signs of pulmonary disease and failure to respond to medical treatment. CLINICAL FINDINGS: At examination, radiography of the thorax revealed increased pulmonary opacity and air bronchograms in the right caudal lung lobe, and radiography of the forelimbs revealed periosteal bone production typical of hypertrophic osteopathy. Attempts to isolate a causative organism included bacterial culture of bronchoalveolar lavage fluid and a lung tissue specimen obtained via fine-needle aspiration. Despite a cytologic diagnosis of septic suppurative inflammation in the lavage fluid, those specimens did not yield bacterial growth. However, a biopsy specimen obtained during a lung lobectomy procedure yielded growth of Eikenella corrodens. TREATMENT AND OUTCOME: Despite successful surgical removal of the consolidated lung lobe and initiation of antimicrobial treatment, the dog died 6 days after surgery. CLINICAL RELEVANCE: The authors are not aware of reports of pulmonary infection with E. corrodens in animals. Infection with the organism is rare, but it is possible that infections are underreported given that the organism is difficult to culture and biopsy may be necessary to obtain enough tissue to yield a diagnosis.

Effect of antiviral treatment with entecavir on age- and dose-related outcomes of duck hepatitis B virus infection.

Entecavir (ETV), a potent inhibitor of the hepadnaviral polymerases, prevented the development of persistent infection when administered in the early stages of duck hepatitis B virus (DHBV) infection. In a preliminary experiment, ETV treatment commenced 24 h before infection showed no significant advantage over simultaneous ETV treatment and infection. In two further experiments 14-day-old ducks were inoculated with DHBV-positive serum containing 10(4), 10(6), 10(8), or 5 x 10(8) viral genomes (vge) and were treated orally with 1.0 mg/kg of body weight/day of ETV for 14 or 49 days. A relationship between virus dose and infection outcome was seen: non-ETV-treated ducks inoculated with 10(4) vge had transient infection, while ducks inoculated with higher doses developed persistent infection. ETV treatment for 49 days did not prevent initial infection of the liver but restricted the spread of infection more than approximately 1,000-fold, a difference which persisted throughout treatment and for up to 49 days after withdrawal. Ultimately, three of seven ETV-treated ducks resolved their DHBV infection, while the remaining ducks developed viremia and persistent infection after a lag period of at least 63 days. ETV treatment for 14 days also restricted the spread of infection, leading to marked and sustained reductions in the number of DHBV-positive hepatocytes in 7 out of 10 ducks. In conclusion, short-term suppression with ETV provides opportunity for the immune response to successfully control DHBV infection. Since DHBV infection of ducks provides a good model system for HBV infection in humans, it seems likely that ETV may be useful in postexposure therapy for HBV infection aimed at preventing the development of persistent infection.

Covalently closed circular DNA is the predominant form of duck hepatitis B virus DNA that persists following transient infection.

Residual hepatitis B virus (HBV) DNA can be detected in serum and liver after apparent recovery from transient infection. However, it is not known if this residual HBV DNA represents ongoing viral replication and antigen expression. In the current study, ducks inoculated with duck hepatitis B virus (DHBV) were monitored for residual DHBV DNA following recovery from transient infection until 9 months postinoculation (p.i.). Resolution of DHBV infection occurred in 13 out of 15 ducks by 1-month p.i., defined as clearance of DHBV surface antigen-positive hepatocytes from the liver and development of anti-DHBV surface antibodies. At 9 months p.i., residual DHBV DNA was detected using nested PCR in 10/11 liver, 7/11 spleen, 2/11 kidney, 1/11 heart, and 1/11 adrenal samples. Residual DHBV DNA was not detected in serum or peripheral blood mononuclear cells. Within the liver, levels of residual DHBV DNA were 0.0024 to 0.016 copies per cell, 40 to 80% of which were identified as covalently closed circular viral DNA by quantitative PCR assay. This result, which was confirmed by Southern blot hybridization, is consistent with suppressed viral replication or inactive infection. Samples of liver and spleen cells from recovered animals did not transmit DHBV infection when inoculated into 1- to 2-day-old ducklings, and immunosuppressive treatment of ducks with cyclosporine and dexamethasone for 4 weeks did not alter levels of residual DHBV DNA in the liver. These findings further characterize a second form of hepadnavirus persistence in a suppressed or inactive state, quite distinct from the classical chronic carrier state.

Entecavir therapy combined with DNA vaccination for persistent duck hepatitis B virus infection.

This study was designed to test the efficacy of antiviral treatment with entecavir (ETV) in combination with DNA vaccines expressing duck hepatitis B virus (DHBV) antigens as a therapy for persistent DHBV infection in ducks. Ducks were inoculated with 10(9) DHBV genomes at 7 days of age, leading to widespread infection of the liver and viremia within 7 days, and were then treated orally with either ETV (0.1 mg/kg of body weight/day) or distilled water from 21 days posthatch for 244 days. Treatment with ETV caused a 4-log drop in serum DHBV DNA levels within 80 days and a slower 2- to 3-log drop in serum DHBV surface antigen (DHBsAg) levels within 120 days. Following withdrawal of ETV, levels of serum DHBV DNA and DHBsAg rebounded to match those in the water-treated animals within 40 days. Sequential liver biopsy samples collected throughout the study showed that ETV treatment reduced DHBV DNA replicative intermediates 70-fold in the liver, while the level of the stable, template form, covalently closed circular DNA decreased only 4-fold. ETV treatment reduced both the intensity of antigen staining and the percentage of antigen-positive hepatocytes in the liver, but the intensity of antigen staining in bile duct cells appeared not to be effected. Intramuscular administration of five doses of a DNA vaccine expressing the DHBV presurface, surface, precore, and core antigens, both alone and concurrently with ETV treatment, on days 50, 64, 78, 127, and 141 did not result in any significant effect on viral markers.