Neurologic disease in captive lions (Panthera leo) with low-titer lion lentivirus infection

Management of Suspected Cases of Feline Immunodeficiency Virus Infection in Eurasian Lynx (Lynx lynx) During an International Translocation Program

The Eurasian lynx (Lynx lynx) population in Switzerland serves as a source for reintroductions in neighboring countries. In 2016–2017, three lynx from the same geographical area were found seropositive for feline immunodeficiency virus (FIV) in the framework of an international translocation program. This novel finding raised questions about the virus origin and pathogenicity to lynx, the emerging character of the infection, and the interpretation of serological results in other lynx caught for translocation. Archived serum samples from 84 lynx captured in 2001–2016 were retrospectively tested for FIV antibodies by Western blot. All archived samples were FIV-negative. The three seropositive lynx were monitored in quarantine enclosures prior to euthanasia and necropsy. They showed disease signs, pathological findings, and occurrence of co-infections reminding of those described in FIV-infected domestic cats. All attempts to isolate and characterize the virus failed but serological data and spatiotemporal proximity of the cases suggested emergence of a lentivirus with antigenic and pathogenic similarities to FIV in the Swiss lynx population. A decision scheme was developed to minimize potential health risks posed by FIV infection, both in the recipient and source lynx populations, considering conservation goals, animal welfare, and the limited action range resulting from local human conflicts. Development and implementation of a cautious decision scheme was particularly challenging because FIV pathogenic potential in lynx was unclear, negative FIV serological results obtained within the first weeks after infection are unpredictable, and neither euthanasia nor repatriation of multiple lynx was acceptable options. The proposed scheme distinguished between three scenarios: release at the capture site, translocation, or euthanasia. Until April 2021, none of the 40 lynx newly captured in Switzerland tested FIV-seropositive. Altogether, seropositivity to FIV was documented in none of 124 lynx tested at their first capture, but three of them seroconverted in 2016–2017. Diagnosis of FIV infection in the three seropositive lynx remains uncertain, but clinical observations and pathological findings confirmed that euthanasia was appropriate. Our experiences underline the necessity to include FIV in pathogen screenings of free-ranging European wild felids, the importance of lynx health monitoring, and the usefulness of health protocols in wildlife translocation.

A pilot study evaluating the utility of commercially available antibodies for flow cytometric analysis of Panthera species lymphocytes

Background

The immune response against tuberculosis in lions is still poorly defined and our understanding is hampered by the lack of lion specific reagents. The process for producing antibodies against a specific antigen is laborious and not available to many research laboratories. As the search for antibody cross-reactivity is an important strategy for immunological studies in veterinary medicine, we have investigated the use of commercially available antibodies to characterize T cell subsets in African lions (Panthera leo).

Results

Commercially available antibodies were screened and investigated the influence of two different sample processing methods, as well as the effect of time delay on cell surface marker expression on lion lymphocytes. Using commercially available antibodies, we were able to identify CD4⁺, CD5⁺, CD8⁺, CD14⁺, CD25⁺, CD44⁺ and CD45⁺ T lymphocytes in samples obtained by density gradient centrifugation as well as red cell lysis of lion whole blood. Two distinct lymphocyte populations, which differed in size and phenotype, were observed in the samples processed by density gradient centrifugation.

Conclusion

Commercially available antibodies are able to differentiate between T lymphocyte subsets including immune effector cells in African lion whole blood, and possibly give insight into unique specie phenotypes.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1717-4) contains supplementary material, which is available to authorized users.

Role of Feline Immunodeficiency Virus in Lymphomagenesis--Going Alone or Colluding?

Feline immunodeficiency virus (FIV) is a naturally occurring lentivirus of domestic and nondomestic feline species. Infection in domestic cats leads to immune dysfunction via mechanisms similar to those caused by human immunodeficiency virus (HIV) and, as such, is a valuable natural animal model for acquired immunodeficiency syndrome (AIDS) in humans. An association between FIV and an increased incidence of neoplasia has long been recognized, with frequencies of up to 20% in FIV-positive cats recorded in some studies. This is similar to the rate of neoplasia seen in HIV-positive individuals, and in both species neoplasia typically requires several years to arise. The most frequently reported type of neoplasia associated with FIV infection is lymphoma. Here we review the possible mechanisms involved in FIV lymphomagenesis, including the possible involvement of coinfections, notably those with gamma-herpesviruses.

Three pathogens in sympatric populations of pumas, bobcats, and domestic cats: implications for infectious disease transmission

Anthropogenic landscape change can lead to increased opportunities for pathogen transmission between domestic and non-domestic animals. Pumas, bobcats, and domestic cats are sympatric in many areas of North America and share many of the same pathogens, some of which are zoonotic. We analyzed bobcat, puma, and feral domestic cat samples collected from targeted geographic areas. We examined exposure to three pathogens that are taxonomically diverse (bacterial, protozoal, viral), that incorporate multiple transmission strategies (vector-borne, environmental exposure/ingestion, and direct contact), and that vary in species-specificity. Bartonella spp., Feline Immunodeficiency Virus (FIV), and Toxoplasma gondii IgG were detected in all three species with mean respective prevalence as follows: puma 16%, 41% and 75%; bobcat 31%, 22% and 43%; domestic cat 45%, 10% and 1%. Bartonella spp. were highly prevalent among domestic cats in Southern California compared to other cohort groups. Feline Immunodeficiency Virus exposure was primarily associated with species and age, and was not influenced by geographic location. Pumas were more likely to be infected with FIV than bobcats, with domestic cats having the lowest infection rate. Toxoplasma gondii seroprevalence was high in both pumas and bobcats across all sites; in contrast, few domestic cats were seropositive, despite the fact that feral, free ranging domestic cats were targeted in this study. Interestingly, a directly transmitted species-specific disease (FIV) was not associated with geographic location, while exposure to indirectly transmitted diseases – vector-borne for Bartonella spp. and ingestion of oocysts via infected prey or environmental exposure for T. gondii – varied significantly by site. Pathogens transmitted by direct contact may be more dependent upon individual behaviors and intra-specific encounters. Future studies will integrate host density, as well as landscape features, to better understand the mechanisms driving disease exposure and to predict zones of cross-species pathogen transmission among wild and domestic felids.

Emerging viruses in the Felidae: shifting paradigms

The domestic cat is afflicted with multiple viruses that serve as powerful models for human disease including cancers, SARS and HIV/AIDS. Cat viruses that cause these diseases have been studied for decades revealing detailed insight concerning transmission, virulence, origins and pathogenesis. Here we review recent genetic advances that have questioned traditional wisdom regarding the origins of virulent Feline infectious peritonitis (FIP) diseases, the pathogenic potential of Feline Immunodeficiency Virus (FIV) in wild non-domestic Felidae species, and the restriction of Feline Leukemia Virus (FeLV) mediated immune impairment to domestic cats rather than other Felidae species. The most recent interpretations indicate important new evolutionary conclusions implicating these deadly infectious agents in domestic and non-domestic felids.

Feline immunodeficiency virus: disease association versus causation in domestic and nondomestic felids

Feline immunodeficiency virus (FIV) is an important infection in both domestic and nondomestic cats. Although many studies have provided insight into FIV pathophysiology and immunologic responses to infection in cats, questions remain regarding the association of FIV with specific disease syndromes. For many diseases, both association and causation of disease with FIV remain to be confirmed and clarified. The use of experimental infection models is unlikely to yield answers about naturally infected domestic cats and is not feasible in nondomestic felids, many of which are endangered species. Researches might consider further study of naturally occurring disease with an emphasis on confirming which diseases have a likely association with FIV.

FIV diversity: FIV Ple subtype composition may influence disease outcome in African lions

Feline immunodeficiency virus (FIV) infects domestic cats and at least 20 additional species of non-domestic felids throughout the world. Strains specific to domestic cat (FIV(Fca)) produce AIDS-like disease progression, sequelae and pathology providing an informative model for HIV infection in humans. Less is known about the immunological and pathological influence of FIV in other felid species although multiple distinct strains of FIV circulate in natural populations. As in HIV-1 and HIV-2, multiple diverse cross-species infections may have occurred. In the Serengeti National Park, Tanzania, three divergent subtypes of lion FIV (FIV(Ple)) are endemic, whereby 100% of adult lions are infected with one or more of these strains. Herein, the relative distribution of these subtypes in the population are surveyed and, combined with observed differences in lion mortality due to secondary infections based on FIV(Ple) subtypes, the data suggest that FIV(Ple) subtypes may have different patterns of pathogenicity and transmissibility among wild lion populations.

Illness as a source of variation of laterality in lions (Panthera leo)

Brain asymmetry--i.e. the specialisation of each cerebral hemisphere for sensorimotor processing mechanisms and for specific cognitive functions-is widely distributed among vertebrates. Several factors, such as embryological manipulations, sex, age, and breeds, can influence the maintenance, strength, and direction of laterality within a certain vertebrate species. Brain lateralisation is a universal phenomenon characterising not only cerebral control of cognitive or emotion-related functions but also cerebral regulation of somatic processes, and its evolution is strongly influenced by social selection pressure. Diseases are well known to be a cost of sociality but their role in influencing behaviour has received very little attention. The present study investigates the influence of illness conditions as a source of variation on laterality in a social keystone vertebrate predator model, the lion. In a preliminary stage, the clinical conditions of 24 adult lions were assessed. The same animals were scored for forelimb preference when in the quadrupedal standing position. Lions show a marked forelimb preference with a population bias towards the use of the right forelimb. Illness conditions strongly influenced the strength of laterality bias, with a significant difference between clinically healthy and sick lions. According to these results, health conditions should be recognised as an important source of variation in brain lateralisation.

Molecular epidemiology of feline immunodeficiency virus in the domestic cat (Felis catus)

Studying the evolutionary mechanisms of feline immunodeficiency virus in the domestic cat (Felis catus), FIV(Fca), provides a good comparison to other lentiviruses, such as HIV and FIV(Pco) in the cougar (Puma concolor). We review the current epidemiological and evolutionary findings of FIV(Fca). In addition to the five accepted FIV(Fca), subtypes, several recent phylogenetic studies have found strains that form separate clades, indicative of novel subtypes. In New Zealand cats, these strains of unknown subtype have been found to be involved in complex patterns of intergenic recombination, and whole genome sequences are required to resolve these. Evidence of recombination events has been documented with the highest levels in the env gene, the region involved in host cell receptor recognition. Several cases of FIV(Fca) multiple infections, both inter- and intra-subtype, have been reported. The findings of both unknown subtypes and relatively high levels of recombination suggest the need for further testing of the current vaccine. Limited studies on the evolutionary rate of FIV(Fca) document a value twice to three times that of FIV in the cougar, a result suggesting the different levels of co-adaptation between the viruses and their respective hosts. We studied the tissue distribution of FIV(Fca) in feral domestic cats, finding the first case of FIV compartmentalisation, a phenomenon well documented in HIV-1 patients.

Pathological manifestations of feline immunodeficiency virus (FIV) infection in wild African lions

Feline immunodeficiency virus (FIV) causes AIDS in the domestic cat (Felis catus) but has not been explicitly associated with AIDS pathology in any of the eight free-ranging species of Felidae that are endemic with circulating FIV strains. African lion (Panthera leo) populations are infected with lion-specific FIV strains (FIVple), yet there remains uncertainty about the degree to which FIV infection impacts their health. Reported CD4+ T-lymphocyte depletion in FIVple-infected lions and anecdotal reports of lion morbidity associated with FIV seroprevalence emphasize the concern as to whether FIVple is innocuous or pathogenic. Here we monitored clinical, biochemical, histological and serological parameters among FIVple-positive (N=47) as compared to FIVple-negative (N=17) lions anesthetized and sampled on multiple occasions between 1999 and 2006 in Botswana. Relative to uninfected lions, FIVple-infected lions displayed a significant elevation in the prevalence of AIDS-defining conditions: lymphadenopathy, gingivitis, tongue papillomas, dehydration, and poor coat condition, as well as displaying abnormal red blood cell parameters, depressed serum albumin, and elevated liver enzymes and gamma globulin. Spleen and lymph node biopsies from free-ranging FIVple-infected lions (N=9) revealed evidence of lymphoid depletion, the hallmark pathology documented in immunodeficiency virus infections of humans (HIV-1), macaques, and domestic cats. We conclude that over time FIVple infections in free-ranging lions can lead to adverse clinical, immunological, and pathological outcomes in some individuals that parallel sequelae caused by lentivirus infection in humans (HIV), Asian macaques (SIV) and domestic cats (FIVfca).

Ocelots on Barro Colorado Island are infected with feline immunodeficiency virus but not other common feline and canine viruses

Transmission of pathogens from domestic animals to wildlife populations (spill-over) has precipitated local wildlife extinctions in multiple geographic locations. Identifying such events before they cause population declines requires differentiating spillover from endemic disease, a challenge complicated by a lack of baseline data from wildlife populations that are isolated from domestic animals. We tested sera collected from 12 ocelots (Leopardus pardalis) native to Barro Colorado Island, Panama, which is free of domestic animals, for antibodies to feline herpes virus, feline calicivirus, feline corona virus, feline panleukopenia virus, canine distemper virus, and feline immunodeficiency virus (FIV), typically a species-specific infection. Samples also were tested for feline leukemia virus antigens. Positive tests results were only observed for FIV; 50% of the ocelots were positive. We hypothesize that isolation of this population has prevented introduction of pathogens typically attributed to contact with domestic animals. The high density of ocelots on Barro Colorado Island may contribute to a high prevalence of FIV infection, as would be expected with increased contact rates among conspecifics in a geographically restricted population.

Could FIV zoonosis responsible of the breakdown of the pathocenosis which has reduced the European CCR5-Delta32 allele frequencies?

Background

In Europe, the north-south downhill cline frequency of the chemokine receptor CCR5 allele with a 32-bp deletion (CCR5-Δ32) raises interesting questions for evolutionary biologists. We had suggested first that, in the past, the European colonizers, principally Romans, might have been instrumental of a progressively decrease of the frequencies southwards. Indeed, statistical analyses suggested strong negative correlations between the allele frequency and historical parameters including the colonization dates by Mediterranean civilisations. The gene flows from colonizers to native populations were extremely low but colonizers are responsible of the spread of several diseases suggesting that the dissemination of parasites in naive populations could have induced a breakdown rupture of the fragile pathocenosis changing the balance among diseases. The new equilibrium state has been reached through a negative selection of the null allele.

Results

Most of the human diseases are zoonoses and cat might have been instrumental in the decrease of the allele frequency, because its diffusion through Europe was a gradual process, due principally to Romans; and that several cat zoonoses could be transmitted to man. The possible implication of a feline lentivirus (FIV) which does not use CCR5 as co-receptor is discussed. This virus can infect primate cells in vitro and induces clinical signs in macaque. Moreover, most of the historical regions with null or low frequency of CCR5-Δ32 allele coincide with historical range of the wild felid species which harbor species-specific FIVs.

Conclusion

We proposed the hypothesis that the actual European CCR5 allelic frequencies are the result of a negative selection due to a disease spreading. A cat zoonosis, could be the most plausible hypothesis. Future studies could provide if CCR5 can play an antimicrobial role in FIV pathogenesis. Moreover, studies of ancient DNA could provide more evidences regarding the implications of zoonoses in the actual CCR5-Δ32 distribution.

FIV cross-species transmission: an evolutionary prospective

Feline and primate immunodeficiency viruses (FIVs, SIVs, and HIV) are transmitted via direct contact (e.g. fighting, sexual contact, and mother–offspring transmission). This dynamic likely poses a behavioral barrier to cross-species transmission in the wild. Recently, several host intracellular anti-viral proteins that contribute to species-specificity of primate lentiviruses have been identified revealing adaptive mechanisms that further limit spread of lentiviruses between species. Consistent with these inter-species transmission barriers, phylogenetic evidence supports the prediction that FIV transmission is an exceedingly rare event between free-ranging cat species, though it has occurred occasionally in captive settings. Recently we documented that puma and bobcats in Southern California share an FIV strain, providing an opportunity to evaluate evolution of both viral strains and host intracellular restriction proteins. These studies are facilitated by the availability of the 2× cat genome sequence annotation. In addition, concurrent viral and host genetic analyses have been used to track patterns of migration of the host species and barriers to transmission of the virus within the African lion. These studies illustrate the utility of FIV as a model to discover the variables necessary for establishment and control of lentiviral infections in new species.

Frequent transmission of immunodeficiency viruses among bobcats and pumas

With the exception of human immunodeficiency virus (HIV), which emerged in humans after cross-species transmissions of simian immunodeficiency viruses from nonhuman primates, immunodeficiency viruses of the family Lentiviridae represent species-specific viruses that rarely cross species barriers to infect new hosts. Among the Felidae, numerous immunodeficiency-like lentiviruses have been documented, but only a few cross-species transmissions have been recorded, and these have not been perpetuated in the recipient species. Lentivirus seroprevalence was determined for 79 bobcats (Lynx rufus) and 31 pumas (Puma concolor) from well-defined populations in Southern California. Partial genomic sequences were subsequently obtained from 18 and 12 seropositive bobcats and pumas, respectively. Genotypes were analyzed for phylogenic relatedness and genotypic composition among the study set and archived feline lentivirus sequences. This investigation of feline immunodeficiency virus infection in bobcats and pumas of Southern California provides evidence that cross-species infection has occurred frequently among these animals. The data suggest that transmission has occurred in multiple locations and are most consistent with the spread of the virus from bobcats to pumas. Although the ultimate causes remain unknown, these transmission events may occur as a result of puma predation on bobcats, a situation similar to that which fostered transmission of HIV to humans, and likely represent the emergence of a lentivirus with relaxed barriers to cross-species transmission. This unusual observation provides a valuable opportunity to evaluate the ecological, behavioral, and molecular conditions that favor repeated transmissions and persistence of lentivirus between species.

Going wild: lessons from naturally occurring T-lymphotropic lentiviruses

Over 40 nonhuman primate (NHP) species harbor species-specific simian immunodeficiency viruses (SIVs). Similarly, more than 20 species of nondomestic felids and African hyenids demonstrate seroreactivity against feline immunodeficiency virus (FIV) antigens. While it has been challenging to study the biological implications of nonfatal infections in natural populations, epidemiologic and clinical studies performed thus far have only rarely detected increased morbidity or impaired fecundity/survival of naturally infected SIV- or FIV-seropositive versus -seronegative animals. Cross-species transmissions of these agents are rare in nature but have been used to develop experimental systems to evaluate mechanisms of pathogenicity and to develop animal models of HIV/AIDS. Given that felids and primates are substantially evolutionarily removed yet demonstrate the same pattern of apparently nonpathogenic lentiviral infections, comparison of the biological behaviors of these viruses can yield important implications for host-lentiviral adaptation which are relevant to human HIV/AIDS infection. This review therefore evaluates similarities in epidemiology, lentiviral genotyping, pathogenicity, host immune responses, and cross-species transmission of FIVs and factors associated with the establishment of lentiviral infections in new species. This comparison of consistent patterns in lentivirus biology will expose new directions for scientific inquiry for understanding the basis for virulence versus avirulence.