CANINE DISTEMPER VIRUS ANTIBODY TITERS IN DOMESTIC CATS AFTER DELIVERY OF A LIVE ATTENUATED VIRUS VACCINE

Safety and Immunogenicity of Morbillivirus canis Vaccines for Domestic and Wild Animals: A Scoping Review

Morbillivirus canis (canine distemper virus (CDV)) is recognized as a multihost pathogen responsible for a transmissible disease affecting both domestic and wild animals. A considerable portion of wildlife populations remain unvaccinated due to a lack of safety and immunogenicity data on existing vaccines for the prevention of CDV infection in these species. This review aimed to assess the current state of CDV vaccination research for both domestic and wild animals and to explore novel vaccine candidates through in vivo studies. It also sought to synthesize the scattered information from the extensive scientific literature on CDV vaccine research, identify key researchers in the field, and highlight areas where research on CDV vaccination is lacking. A scoping review was conducted across four databases following the PRISMA-ScR protocol, with information analyzed using absolute and relative frequencies and 95% confidence intervals (CIs) for study number proportions. Among the 2321 articles retrieved, 68 met the inclusion criteria and focused on CDV vaccines in various animal species, such as dogs, ferrets, minks, and mice. Most of the scientific community involved in this research was in the USA, Canada, France, and Denmark. Various vaccine types, including MLV CDV, recombinant virus, DNA plasmids, inactivated CDV, and MLV measles virus (MeV), were identified, along with diverse immunization routes and schedules employed in experimental and commercial vaccines. Safety and efficacy data were summarized. Notably, 37 studies reported postimmunization CDV challenge, primarily in dogs, revealing the survival rates of vaccinated animals. In summary, CDV vaccines generally demonstrate an acceptable safety profile in dogs and show promise as a means of controlling CDV. However, significant gaps in vaccine research persist, particularly concerning wildlife reservoirs, indicating the need for further investigation.

TIGER (PANTHERA TIGRIS) AND DOMESTIC CAT (FELIS CATUS) IMMUNE RESPONSES TO CANARYPOX-VECTORED CANINE DISTEMPER VACCINATION

Two methods for delivering a canarypox-vectored canine distemper vaccine to tigers (Panthera tigris) and domestic cats (Felis catus) were investigated. Eight tigers were divided randomly into two vaccination groups: subcutaneous injection or topical tonsillar application. Each tiger received 2 ml of canine distemper virus (CDV) vaccine (Merial Ferret Distemper Vaccine). Blood was collected from tigers on days 0, 21, 35 or 37, and 112 post-initial vaccination (PIV). Domestic cats were divided randomly into four treatment groups: saline injection (negative controls), low- and high-dose oral, and subcutaneous vaccinates. Blood was collected from domestic cats on days 0, 7, 21, and 28 and 165 or 208 PIV. Sera were tested for CDV antibodies by virus neutralization. All individuals were seronegative at the beginning of the study. One tiger vaccinated subcutaneously developed a titer of 32 by day 35, which reduced to 16 by day 112. Another tiger vaccinated by tonsillar application developed a titer of 8 on day 112. All other tigers remained seronegative. Cats that received saline injection or oral vaccination remained seronegative at each sampling time. Domestic cats vaccinated subcutaneously developed titers ranging from 4 to >128 by day 28, and those re-bled at day 166 had titers of 16 or 64. The disparity in response between domestic cats and tigers may be due to species differences or it may represent a dose-dependent effect. Subcutaneous vaccination with canarypox-vectored Purevax Ferret Distemper^® is safe and elicits persistent antibody titers in domestic cats vaccinated parenterally.

Assessing the health risks of reintroduction: The example of the Amur leopard, Panthera pardus orientalis

Translocation of wildlife as a means of reintroducing or reinforcing threatened populations is an important conservation tool but carries health risks for the translocated animals and their progeny, as well as wildlife, domestic animals and humans in the release area. Disease risk analyses (DRA) are used to identify, prioritize and design mitigation strategies to address these threats. Here, we use a DRA undertaken for Amur leopards (Panthera pardus orientalis) to illustrate how specific methodology can optimize mitigation strategy design. A literature review identified a total of 98 infectious hazards and 28 non-infectious hazards. Separate analyses were undertaken for disease risks in leopards from hazards of source origin (captive zoo collections and the transit pathway to the Russian Far East), or of destination origin (in breeding enclosures and wider release areas); and for disease risks in other wildlife, domesticated species or humans, similarly from hazards of source or destination origin. Hazards were assessed and ranked as priority 1, priority 2, priority 3 or low priority in each of the defined scenarios. In addition, we undertook a generic assessment of stress on individual leopards. We use three examples to illustrate the process: Chlamydophila felis, canine distemper virus (CDV) and feline immunodeficiency virus (FIV). We found that many potentially expensive screening procedures could be performed prior to export of leopards, putting the onus of responsibility onto the zoo sector, for which access to diagnostic testing facilities is likely to be optimal. We discuss how our methods highlighted significant data gaps relating to pathogen prevalence in the Russian Far East and likely future unpredictability, in particular with respect to CDV. There was emphasis at all stages on record keeping, meticulous planning, design, staff training and enclosure management, which are relatively financially inexpensive. Actions to minimize stress featured at all time points in the strategy and also focussed on planning, design and management.

Outbreak and genotyping of canine distemper virus in captive Siberian tigers and red pandas

In this study, four canine distemper virus (CDV) strains were isolated from captive Siberian tigers (Panthera tigris altaica) and red pandas (Ailurus fulgens) during two separate CDV outbreaks in a zoo in Guangdong province, China. Sequence alignment and phylogenetic analyses based on the full-length hemagglutinin (H) and fusion (F) genes showed that they were closely identical to genotype Asia-1. Prior to confirmation of CDV in Siberian tigers, to control spread of the disease, a live attenuated combination CDV vaccine was used among almost all carnivore animals except for red pandas in which another recombinant combination CDV vaccine was used. However, about two months later, CDV re-emerged and caused the death among red pandas. Based on the vaccination records, the live combination vaccine could be considered an ideal weapon against CDV in zoo carnivore animals. Although the recombinant combination CDV vaccine was safe for red pandas, its protection effectiveness remains to be further investigated. Moreover, according to the outbreak interval time and sequence characterization, we suspected that stray cats circulating in the zoo were the intermediate host, which contributed to CDV spread from stray dogs to zoo animals. This study revealed the importance of vaccination and biosecurity for zoo animals.