Thymoma related myasthenia gravis in humans and potential animal models

Thymoma-associated Myasthenia gravis (TAMG) is one of the anti-acetylcholine receptor MG (AChR-MG) subtypes. The clinico-pathological features of TAMG and its pathogenesis are described here in comparison with pathogenetic models suggested for the more common non-thymoma AChR-MG subtypes, early onset MG and late onset MG. Emphasis is put on the role of abnormal intratumorous T cell selection and activation, lack of intratumorous myoid cells and regulatory T cells as well as deficient expression of the autoimmune regulator (AIRE) by neoplastic thymic epithelial cells. We review spontaneous and genetically engineered thymoma models in a spectrum of animals and the extensive clinical and immunological overlap between canine, feline and human TAMG. Finally, limitations and perspectives of the transplantation of human and murine thymoma tissue into nude mice, as potential models for TAMG, are addressed.

Lethal infection by a novel reassortant H5N1 avian influenza A virus in a zoo-housed tiger

In early 2013, a Bengal tiger (Panthera tigris) in a zoo died of respiratory distress. All specimens from the tiger were positive for HPAI H5N1, which were detected by real-time PCR, including nose swab, throat swab, tracheal swab, heart, liver, spleen, lung, kidney, aquae pericardii and cerebrospinal fluid. One stain of virus, A/Tiger/JS/1/2013, was isolated from the lung sample. Pathogenicity experiments showed that the isolate was able to replicate and cause death in mice. Phylogenetic analysis indicated that HA and NA of A/Tiger/JS/1/2013 clustered with A/duck/Vietnam/OIE-2202/2012 (H5N1), which belongs to clade 2.3.2.1. Interestingly, the gene segment PB2 shared 98% homology with A/wild duck/Korea/CSM-28/20/2010 (H4N6), which suggested that A/Tiger/JS/1/2013 is a novel reassortant H5N1 subtype virus. Immunohistochemical analysis also confirmed that the tiger was infected by this new reassortant HPAI H5N1 virus. Overall, our results showed that this Bengal tiger was infected by a novel reassortant H5N1, suggesting that the H5N1 virus can successfully cross species barriers from avian to mammal through reassortment.

Zoonotic and vector-borne pathogens in tigers from a wildlife safari park, Italy

Infectious diseases by pathogens, including those of zoonotic concern, may act as a primary or contributory cause of threat to wildlife conservation and may represent a risk for human health, mainly for people working at, or visiting the zoological parks. Given the paucity of data on pathogens infecting wild tigers, we investigated the occurrence of infectious agents in this animal species, with a special focus on those of zoonotic concern. Blood and serum samples from tigers (n = 20) living in a wildlife safari park of southern Italy were screened by serological and molecular tests. All animals scored positive for antibodies against Toxoplasma gondii (100%), whereas they displayed different prevalence of seropositivity for Rickettsia conorii (30%), Bartonella henselae (15%) and Leptospira interrogans sv Icterohaemorrhagiae and/or Leptospira kirschneri sv Grippotyphosa (15%). No antibodies against Coxiella burnetii were detected. In addition, 8 tigers (40%) tested molecularly positive to "Candidatus Mycoplasma haemominutum", and 3 (15%) to Hepatozoon canis. No DNA of R. conorii, Bartonella spp., Ehrlichia/Anaplasma spp. and piroplasmids was amplified. The occurrence of tiger infections by bacteria and parasites may represent a risk for morbidity and, in some circumstances, mortality in this endangered species and a source of infection for other animals, including humans. These findings indicate that the circulation of zoonotic pathogens such as T. gondii, R. conorii, L. interrogans sv Icterohaemorrhagiae, "Candidatus Mycoplasma haemominutum" and B. henselae in given environments may represent a relevant health issue considering the close association among animals and humans visiting, or working at, the wildlife safari park. Preventative measures are advocated in order to control ectoparasites and other sources of infection (e.g., small rodents), thus for minimizing the risk of infection for animals as well as for humans.

Pioneer identification of fake tiger claws using morphometric and DNA-based analysis in wildlife forensics in India

The illegal trade in wildlife is a serious threat to the existence of wild animals throughout the world. The short supply and high demand for wildlife articles have caused an influx of many different forms of fake wildlife articles into this trade. The task of identifying the materials used in making such articles poses challenges in wildlife forensics as different approaches are required for species identification. Claws constitute 3.8% of the illegal animal parts (n=2899) received at the Wildlife Institute of India (WII) for species identification. We describe the identification of seized suspected tiger claws (n=18) using a combined approach of morphometric and DNA-based analysis. The differential keratin density, determined using X-ray radiographs, indicated that none of the 18 claws were of any large cat but were fake. We determined three claw measurements, viz. ac (from the external coronary dermo-epidermal interface to the epidermis of the skin fold connecting the palmar flanges of the coronary horn), bc (from the claw tip to the epidermis of the skin fold connecting the palmar flanges of the coronary horn) and the ratio bc/ac, for all the seized (n=18), tiger (n=23) and leopard (n=49) claws. Univariate and multivariate statistical analyses were performed using SPSS. A scatter plot generated using canonical discriminant function analysis revealed that of the 18 seized claws, 14 claws formed a cluster separate from the clusters of the tiger and leopard claws, whereas the remaining four claws were within the leopard cluster. Because a discrepancy was observed between the X-ray images and the measurements of these four claws, one of the claw that clustered with the leopard claws was chosen randomly and DNA analysis carried out using the cyt b (137bp) and 16S rRNA (410bp) genes. A BLAST search and comparison with the reference database at WII indicated that the keratin material of the claw was derived from Bos taurus (cattle). This is a pioneering discovery, and we suggest that a hierarchical combination of techniques be used for identifying claws involved in wildlife offences, i.e. that an X-ray, morphometric and DNA-based analysis be carried out, to ascertain whether the claws are of tigers or leopards. To identify species in the illegal wildlife trade morphometric and genetic reference database should be developed. Morphological features as well as DNA profiles need to be used for better implementation of the Wildlife (Protection) Act, 1972 of India and other laws/treaties in South-east Asia.

Assessment of fine-scale resource selection and spatially explicit habitat suitability modelling for a re-introduced tiger (Panthera tigris) population in central India

BACKGROUND

Large carnivores influence ecosystem functions at various scales. Thus, their local extinction is not only a species-specific conservation concern, but also reflects on the overall habitat quality and ecosystem value. Species-habitat relationships at fine scale reflect the individuals' ability to procure resources and negotiate intraspecific competition. Such fine scale habitat choices are more pronounced in large carnivores such as tiger (Panthera tigris), which exhibits competitive exclusion in habitat and mate selection strategies. Although landscape level policies and conservation strategies are increasingly promoted for tiger conservation, specific management interventions require knowledge of the habitat correlates at fine scale.

METHODS

We studied nine radio-collared individuals of a successfully reintroduced tiger population in Panna Tiger Reserve, central India, focussing on the species-habitat relationship at fine scales. With 16 eco-geographical variables, we performed Manly's selection ratio and K-select analyses to define population-level and individual-level variation in resource selection, respectively. We analysed the data obtained during the exploratory period of six tigers and during the settled period of eight tigers separately, and compared the consequent results. We further used the settled period characteristics to model and map habitat suitability based on the Mahalanobis D² method and the Boyce index.

RESULTS

There was a clear difference in habitat selection by tigers between the exploratory and the settled period. During the exploratory period, tigers selected dense canopy and bamboo forests, but also spent time near villages and relocated village sites. However, settled tigers predominantly selected bamboo forests in complex terrain, riverine forests and teak-mixed forest, and totally avoided human settlements and agriculture areas. There were individual variations in habitat selection between exploratory and settled periods. Based on threshold limits of habitat selection by the Boyce Index, we established that 83% of core and 47% of buffer areas are now suitable habitats for tiger in this reserve.

DISCUSSION

Tiger management often focuses on large-scale measures, but this study for the first time highlights the behaviour and fine-scale individual-specific habitat selection strategies. Such knowledge is vital for management of critical tiger habitats and specifically for the success of reintroduction programs. Our spatially explicit habitat suitability map provides a baseline for conservation planning and optimizing carrying capacity of the tiger population in this reserve.

Muscular anatomy of the forelimb of tiger (Panthera tigris)

Dissection reports of large cats (family Felidae) have been published since the late 19th century. These reports generally describe the findings in words, show drawings of the dissection, and usually include some masses of muscles, but often neglect to provide muscle maps showing the precise location of bony origins and insertions. Although these early reports can be highly useful, the absence of visual depictions of muscle attachment sites makes it difficult to compare muscle origins and insertions in living taxa and especially to reconstruct muscle attachments in fossil taxa. Recently, more muscle maps have been published in the primary literature, but those for large cats are still limited. Here, we describe the muscular anatomy of the forelimb of the tiger (Panthera tigris), and compare muscle origins, insertions, and relative muscle masses to other felids to identify differences that may reflect functional adaptations. Our results reiterate the conservative nature of felid anatomy across body sizes and behavioral categories. We find that pantherines have relatively smaller shoulder muscle masses, and relatively larger muscles of the caudal brachium, pronators, and supinators than felines. The muscular anatomy of the tiger shows several modifications that may reflect an adaptation to terrestrial locomotion and a preference for large prey. These include in general a relatively large m. supraspinatus (shoulder flexion), an expanded origin for m. triceps brachii caput longum, and relatively large m. triceps brachii caput laterale (elbow extension), as well as relatively large mm. brachioradialis, abductor digiti I longus, and abductor digiti V. Muscle groups that are well developed in scansorial taxa are not well developed in the tiger, including muscles of the cranial compartment of the brachium and antebrachium, and m. anconeus. Overall, the musculature of the tiger strongly resembles that of the lion (Panthera leo), another large-bodied terrestrial large-prey specialist.

Identification of feline Kiss1 and distribution of immunoreactive kisspeptin in the hypothalamus of the domestic cat

In recent years, the Kiss1 gene has been reported in a number of vertebrate species, and a substantial dataset has been acquired to demonstrate the critical role of kisspeptins in the reproductive system; yet limited information is available for carnivores. In the present study, we identified and characterized feline Kiss1 by isolating and cloning its full-length cDNA in the domestic cat hypothalamus and caracal testis, using the method of rapid amplification of cDNA ends. Additionally, we isolated and cloned the 3′ end of Kiss1 cDNA, containing kisspeptin-10 (Kp10), from the ovaries of a clouded leopard and Siberian tiger. Nucleotide sequencing revealed that domestic cat Kiss1 cDNA is of 711 base pairs and caracal Kiss1 cDNA is of 792 base pairs, both having an open reading frame of 450 base pairs, encoding a precursor protein Kiss1 of 149 amino acids. The core sequence of the feline kisspeptin Kp10 was found to be identical in all species analyzed here and is highly conserved in other vertebrate species. Using an anti-Kp10 antibody, we found the immunoreactive kisspeptin to be localized in the periventricular and infundibular nuclei of the cat hypothalamus. The results show that kisspeptin is highly conserved among different feline families, and its immunoreactive distribution in the hypothalamus may indicate its physiological function in the domestic cat.

Clinical, haematological and biochemical findings in tigers infected by Leishmania infantum

Background

A large number of animal species are susceptible to Leishmania infantum (Kinetoplastida, Trypanosomatidae) in endemic areas, including domestic and wild felids such as tigers (Panthera tigris). Knowledge on the infection of this endangered species is still at its infancy, and therefore this study aims to identify clinical presentation and clinicopathological findings of tigers naturally infected by L. infantum.

Results

Tigers either L. infantum-positive (group A) or -negative (group B) were apparently healthy or presented visceral leishmaniasis unrelated conditions, except for one animal in which a large non-healing cutaneous lesion was observed. However, histological exam and immunohistochemistry carried out on the lesion excluded the presence of L. infantum amastigotes. Biochemical analysis showed that the average concentration of total proteins, globulins and haptoglobin were significantly higher (p < 0.01, p = 0.01 and p = 0.02, respectively), while the albumin/globulin ratio significantly lower (p = 0.05) in group A compared with group B. The biochemical alterations were partially confirmed by the serum protein electrophoresis results revealing a significant increase in the total protein value (p = 0.01) and hypergammaglobulinemia (p = 0.03) but an unmodified albumin/globulin ratio in group A.

Conclusions

In this study tigers infected by L. infantum have shown to be mainly asymptomatic. The absence of clinical signs may lead veterinarians to overlook leishmaniasis in animals kept in captivity. Therefore, diagnostic and screening tests as serology should be part of routinely surveillance programs to be performed on tigers in zoological gardens located in endemic areas. Though only few protein-related laboratory abnormalities were recorded in infected animals, they could provide diagnostic clues for a first suspicion of L. infantum infection in tigers. Indeed, considering the high risk of zoonotic transmission in heavily frequented environment as zoos, a prompt diagnosis of L. infantum infection is of pivotal importance.

Evaluating the reliability of media reports for gathering information about illegal wildlife trade seizures

Illegal wildlife trade (IWT) is threatening many species across the world. It is important to better understand the scale and characteristics of IWT to inform conservation priorities and actions. However, IWT usually takes place covertly, meaning that the data on species, trade routes and volumes is limited. This means that conservationists often have to rely on publicly available law enforcement reports of seizures as potential indicators of the magnitude and characteristics of IWT. Still, even these data may be difficult to access, leading conservationists to use media reports of seizures instead. This is the case in countries like Nepal, which have limited capacity in data keeping and reporting, and no centralized data management system. Yet reliance on media reports risks introducing further biases, which are rarely acknowledged or discussed. Here we characterize IWT in Nepal by comparing data from three sources of information on IWT between January 2005 and July 2017: seizure reports from three Nepali national daily newspapers, official seizure records for Kathmandu district, and data on additional enforcement efforts against IWT in Nepal. We found a strong positive correlation between the number of official and media-reported seizures over time, but media under-reported seizure numbers, with 78% of seizures going unreported. Seizures of charismatic, protected species were reported more often and seizure reports involving tigers were most likely to be reported (57%). Media reports appeared to be a good indicator of trends and the species being seized but not overall seizure number, with the media largely underestimating total seizure numbers. Therefore, media reports cannot be solely relied upon when it comes to informing conservation decision-making. We recommend that conservationists triangulate different data sources when using seizure data reported in the media to more rigorously characterise IWT.

The Effects of Choice-Based Design and Management on the Behavior and Space Use of Zoo-Housed Amur Tigers (Panthera tigris altaica)

Choice-based design allows animals in human care opportunities to move at will between multiple interconnected spaces. Some evidence suggests providing environmental choice confers benefits to animals, but there is a dearth of research in this area with large carnivores. To understand the effects of this design strategy on large felids, behavioral and space use data were collected on three Amur tigers housed in a new habitat at Cleveland Metroparks Zoo. Data were collected in two conditions: 1) restricted to a single habitat, and 2) access to two habitats. With choice, tigers were less frequently inactive (p = 0.003), and locomoted more frequently (p = 0.009). They also showed different preferences in space use with choice, and a strong preference for overhead runways between habitats (E* = 0.83, E* = 0.78). These results add to what is known about environmental impacts on zoo animal behavior and suggest this design and management strategy may be effective in conferring positive welfare benefits to tigers and other large carnivores.

Computed tomography and magnetic resonance imaging study of a normal tarsal joint in a Bengal tiger (Panthera tigris)

Background

In this research, using computed tomography (CT) and magnetic resonance imaging (MRI), we provide a thorough description of the standard appearance of a right tarsal joint in a Bengal tiger (Panthera tigris). CT scans were performed using a bone and soft tissue window setting, and three-dimensional surface reconstructed CT images were obtained. The MRI protocol was based on the use of Spin-echo (SE) T1-weighted and Gradient-echo (GE) STIR T2-weighted pulse sequences. Magnetic resonance (MR) images were taken in the transverse, sagittal and dorsal planes. We also performed anatomical dissections to facilitate the interpretation of the different structures of the tarsus joint and allow comparisons with CT and MRI images.

Results

The CT images allowed us to observe differences between the bones and soft tissues of the tarsal joint. When applying the bone window setting, the obtained footage showed the anatomy between the medulla and cortex. Additionally, the trabecular bone was delineated. By contrast, the soft tissue window allowed the main soft tissue structures of the tarsal joint, including ligaments, muscles and tendons, to be differentiated. Footage of the main anatomical structures of the standard tiger tarsus was obtained through MRI. The SE T1-weighted images showed the best evaluation of the cortical, subchondral and trabecular bone of the tibia, fibula, tarsus and metatarsus bones. Nonetheless, the GE STIR T2-weighted images allowed us to better visualize the articular cartilage and synovial fluid. In both MRI pulse sequences, the ligaments and tendons appeared with low signal intensity compared with muscles that were visible with intermediate signal intensity.

Conclusions

The results of this CT and MRI study of the Bengal tiger tarsal joint provide some valuable anatomical information and may be useful for diagnosing disorders in this large non-domestic cat.

Density estimation of tiger and leopard using spatially explicit capture-recapture framework

The conservation of large carnivores often requires precise and accurate estimates of their populations. Being cryptic and occurring at low population densities, obtaining an unbiased population estimate is difficult in large carnivores. To overcome the uncertainties in the conventional capture–recapture (CR) methods used to estimate large carnivore densities, more robust methods such as spatially explicit capture-recapture (SECR) framework are now widely used. We modeled the CR data of tiger (Panthera tigris tigris) and leopard (Panthera pardus fusca) in the SECR framework with biotic and abiotic covariates likely believed to influence their densities. An effort of 2,211 trap nights resulted in the capture of 33 and 38 individual tigers and leopards. A total of 95 and 74 detections of tigers and leopards were achieved using 35 pairs of camera traps. Tiger and leopard density were estimated at 4.71 ± 1.20 (3.05–5.11) and 3.03 ± 0.78 (1.85–4.99) per 100 km². Our results show that leopard density increased with high road density, high terrain ruggedness and habitats with high percentage of cropland and natural vegetation. The tiger density was positively influenced by the mosaic of cropland and natural vegetation. This study provides the first robust density estimates of tiger and leopard within the study area. Our results support the notion that large carnivores can attain moderate densities within human-dominated regions around protected areas relying on domestic livestock. Broader management strategies aimed at maintaining wild prey in the human-dominated areas around protected areas are necessary for large and endangered carnivores’ sustenance in the buffer zones around protected areas.

Understanding the molecular evolution of tiger diversity through DNA barcoding marker ND4 and NADH dehydrogenase complex using computational biology

BACKGROUND

Currently, Tigers (the top predator of an ecosystem) are on the list of endangered species. Thus the need is to understand the tiger's population genomics to design their conservation strategies.

OBJECTIVE

We analyzed the molecular evolution of tiger diversity using NADH dehydrogenase subunit 4 (ND4), a significant electron transport chain component.

METHODS

We have analyzed nucleotide composition and distribution pattern of ND genes, molecular evolution, evolutionary conservation pattern and conserved blocks of NADH, phylogenomics of ND4, and estimating species divergence, etc., using different bioinformatics tools and software, and MATLAB programming and computing environment.

RESULTS

The nucleotide composition and distribution pattern of ND genes in the tiger genome demonstrated an increase in the number of adenine (A) and a lower trend of A+T content in some place of the distribution analysis. However, the observed distributions were not significant (P > 0.05). Evolutionary conservation analysis showed three highly align blocks (186 to 198, 406 to 416, and 527 to 545). On mapping the molecular evolution of ND4 among model species (n = 30), we observed its presence in a broader range of species. ND4 based molecular evolution of tiger diversity and time divergence for a tiger (20 different other species) shows that genus Panthera originated more or less at a similar time.

CONCLUSIONS

The nucleotide composition and nucleotide distribution pattern of tiger ND genes showed the evolutionary pattern and origin of tiger and Panthera lineage concerning the molecular clock, which will help to understand their adaptive evolution.

Glanders outbreak at Tehran Zoo, Iran

BACKGROUND AND OBJECTIVES

In December 2010 four, lions and one tiger died at the Tehran zoo. Out of all samples, Burkholderia mallei (causative agent of Glanders) was isolated just from ulcer sample of the tiger which was imported to Iran from Russia.

MATERIALS AND METHODS

One nasal swab from a tiger and fifteen blood samples with anticoagulant belonging to one tiger and fourteen lions (four dead lions and eleven live lions) were collected and were inoculated directly onto the selective media. The isolate was identified by morphological and biochemical and API BBL tests and PCR using specific primers (Bma- IS407-flip). The standard (Razi Type Culture Collection RTCC: 2375) and tiger isolates were inoculated into 2 guinea pigs. All residue solipeds and carnivores were checked by Malleination test and Complement Fixation (CF) Test respectively.

RESULTS

One isolate of B. mallei was isolated from tiger's nasal swab. Both of B.mallei strains were recovered from inoculated animals. All of solipeds were negative by malleination test, however, 11 lions including 4 dead and 7 live lions out of 14 lions were positive in CF test for Glanders and all were put down by the authorities.

CONCLUSION

Active surveillance of Glanders is essential for solipeds, especially it's more important while being used to feed valuable carnivores like lions and tigers. Therefore, a reliable test like malleination must be carried out twice (first before transferring and one month after quarantine). Both test results should be negative for use for feeding.

Exploiting genomic synteny in Felidae: cross-species genome alignments and SNV discovery can aid conservation management

Background

While recent advances in genomics has enabled vast improvements in the quantification of genome-wide diversity and the identification of adaptive and deleterious alleles in model species, wildlife and non-model species have largely not reaped the same benefits. This has been attributed to the resources and infrastructure required to develop essential genomic datasets such as reference genomes. In the absence of a high-quality reference genome, cross-species alignments can provide reliable, cost-effective methods for single nucleotide variant (SNV) discovery. Here, we demonstrated the utility of cross-species genome alignment methods in gaining insights into population structure and functional genomic features in cheetah (Acinonyx jubatas), snow leopard (Panthera uncia) and Sumatran tiger (Panthera tigris sumatrae), relative to the domestic cat (Felis catus).

Results

Alignment of big cats to the domestic cat reference assembly yielded nearly complete sequence coverage of the reference genome. From this, 38,839,061 variants in cheetah, 15,504,143 in snow leopard and 13,414,953 in Sumatran tiger were discovered and annotated. This method was able to delineate population structure but limited in its ability to adequately detect rare variants. Enrichment analysis of fixed and species-specific SNVs revealed insights into adaptive traits, evolutionary history and the pathogenesis of heritable diseases.

Conclusions

The high degree of synteny among felid genomes enabled the successful application of the domestic cat reference in high-quality SNV detection. The datasets presented here provide a useful resource for future studies into population dynamics, evolutionary history and genetic and disease management of big cats. This cross-species method of variant discovery provides genomic context for identifying annotated gene regions essential to understanding adaptive and deleterious variants that can improve conservation outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07899-2.

Genome-based development of 15 microsatellite markers in fluorescent multiplexes for parentage testing in captive tigers

As one of the most endangered species, tiger (Panthera tigris) inbreeding has become an urgent issue to address. Using a microsatellite (short tandem repeat, STR) identification system, paternity testing may be helpful to avoid inbreeding in captive breeding programs. In this study, we developed a genome-based identification system named tiger pedigree identification multiplex system (TPI-plex). By analyzing the entire tiger genome, 139,967 STR loci were identified and 12.76% of these displayed three to six alleles among three re-sequenced individual tiger genomes. A total of 204 candidate STRs were identified and screened with a reference population containing 31 unrelated captive tigers. Of these, 15 loci were chosen for inclusion in the multiplex panel. The mean allele number and mean expected heterozygosity (He) were 7.3333 and 0.7789, respectively. The cumulative probability of exclusion (CPE) and total probability of discrimination power (TDP) reached 0.999999472 and 0.999999999999995, respectively. The results showed that the TPI-plex system can be applied in routine pedigree identification for captive tigers. We also added a sex identification marker named TAMEL into the TPI-plex for sex determination.

Additional evidence of tigers (Panthera tigris altaica) as intermediate hosts for Toxoplasma gondii through the isolation of viable strains

Toxoplasmosis is one of the most common zoonotic diseases in the world. Felines excrete Toxoplasma gondii oocysts, which play a key role in the transmission of this protozoon. Pathological diagnoses were performed on four carcasses of captive tigers collected from 2019 to 2021 in China, and T. gondii was surveyed using serology, molecular analysis, and aetiology. Striated muscle samples of the tigers (n = 4) were bioassayed in mice. DNA derived from T. gondii tachyzoites was isolated and characterized using PCR-RFLP. The pathological diagnoses revealed that ageing, declined immune function, liver, and kidney failures caused the deaths in the tigers examined. A modified agglutination test (cut-off: 1:25) revealed that IgG antibodies to T. gondii were 100% (4/4) in the captive tigers. Two viable T. gondii strains (TgTigerCHn3 and TgTigerCHn4) were isolated from tiger striated muscles and seeded on the Vero cell culture for further propagation. The genotypes of TgTigerCHn3 and TgTigerCHn4 were ToxoDB#20 and ToxoDB#2, respectively. The two strains were avirulent for Swiss mice, which matched the ROP18 and ROP5 gene alleles of TgtigerCHn3 (3/4) and TgtigerCHn4 (3/3). Few brain tissue cysts (0-213) were observed in the mice after inoculation with TgTigerCHn3 and TgTigerCHn4. This is the first documented isolation of T. gondii ToxoDB#20 and ToxoDB#2 from tigers. The results provide additional direct evidence of tiger as intermediate hosts for T. gondii. Tigers in the zoos may potentially transmit T. gondii to other animals and humans.

Molecular evidence of hepatozoonosis in tigers of Vidarbha region of Maharashtra State of India

BACKGROUND

Hepatozoonosis has been reported in many species around the world. Few incidences have been reported in various species of wild felids. Tigers are endangered large cats and are protected under the Wildlife Protection Act, 1972 under Schedule I. The study was carried out to estimate the positivity rate of hepatozoonosis in tigers of the Vidarbha region of Maharashtra, India.

METHODS

Blood (n = 21) or tissue samples (n = 5) were collected from 26 wild captured / zoo-born or dead tigers during the quarantine period/post-mortem examination. Blood smear examination along with Polymerase Chain Reaction (PCR) studies were conducted for the detection of hepatozoonosis. All the amplicons from the positive samples were purified and sequenced, and the sequences were subjected to nBLAST analysis to detect the species of Hepatozoon. The sequences were deposited into public domain database of National Center for Biotechnology Information (NCBI) and accession numbers were allotted. A phylogenetic study was undertaken to understand the evolutionary lineage of the pathogen. Tissue distribution studies were carried out on tissue samples received during post mortem. A clinical case in a tiger cub was managed and sub-clinical cases were monitored for relapse. Age-wise, sex-wise, region-wise and captive time-wise positivity rate was estimated. The data was analyzed using statistical tools.

RESULTS

A total of 12 tigers were found positive for H. felis during the screening. A clinical case was diagnosed and successfully treated. The age group of 0-3 years reported a positivity rate of 66.66%, and all the cases found positive were reported between the age group of 0-7 years. Males reported a positivity rate of 58.33 per cent, while females reported 35.71%. Taboba and Andhari Tiger Reserve of the state had a positivity rate of 52.94 per cent. However, the statistical analysis for blood parameters and positivity rate by 't' test and Chi-squared test were found to be non-significant.

CONCLUSIONS

An overall positivity rate of 46.15% indicates the wide distribution of hepatozoonosis among wild tigers of the Vidarbha region of Maharashtra, India, which is strategically important considering the gene flow and migration of tigers. Hepatozoonosis can progress to clinical outcomes in young animals and require veterinary intervention. Molecular tools and phylogenetic studies can supplement important data on circulating species of Hepatozoon in the field. Further studies on the clinical management and epidemiology of the infection in wild felids will comprehend the cause of wildlife conservation.

Canine distemper outbreak and laryngeal paralysis in captive tigers (Panthera tigris)

The canine distemper virus (CDV) could infect various wildlife species worldwide. The viral infection in large felids directly impacts wildlife conservation. This study aimed to understand better the burden of CDV outbreaks in captive tiger populations in Thailand and a novel discovery of their clinical signs with a history of CDV exposure. We followed up on their infection from May 2016 to October 2020 with laboratory testing and veterinary medical records. The cumulative morbidity and mortality rates were relatively high. Moreover, 50% of the tigers survived at 2 years after infection. All suspected and confirmed cases of CDV infections were significantly associated with laryngeal inflammation, which developed into paralysis in almost 50% of cases. Altogether, 50% of all tiger cases with chronic infection developed stridor at 314 days after virus infection [95% CI: 302-320]. Therefore, laryngeal paralysis may result from CDV infection and degeneration, potentially affecting the peripheral and central nervous systems. This condition could pose a life-threatening risk to tigers. The virus could spread quickly by contact with bodily excretion among tigers and fomite contamination once it affects a specific population. Implementation of biosecurity measures and vaccination is essential to mitigate the risk of disease spread and infection rates in tiger populations.

Molecular Characterization of Paragonimus westermani from South India

PURPOSE

Paragonimus westermani is the most common lung fluke infecting humans in Asia. This study aimed to molecularly characterize adult P. westermani from the south India (Kerala) using ITS-2, partial 28 S rDNA and partial cox1 gene sequences.

METHODS

Adult flukes were recovered from the lungs of a tiger (Panthera tigris) (n = 10), a jungle cat (Felis chaus) (n = 6) and a domesticated dog (Canis familiaris) (n = 4). ITS-2, partial 28 SrDNA and partial cox1 gene sequences were amplified by polymerase chain reaction and a concatenated phylogenetic tree was constructed with these three marker sequences. Intra-species and inter-species genetic distances were calculated, and haplotype network analysis was performed using partial cox1 gene.

RESULTS

Phylogenetic analysis based on the concatenated tree showed that Kerala isolates formed P. westermani complex with other isolates of P. westermani from India and from other countries. The Kerala isolates were genetically closer to metacercaria morphotype 2 of P. westermani. However, the genetic distance was higher among Indian isolates, indicating significant genetic variation among P. westermani within the complex. In addition, India also exhibited the highest number of haplotypes (n = 8).

CONCLUSIONS

Concatenated phylogenetic analysis of the Indian isolates of P. westermani show them to form P. westermani complex. The parasite exhibits high genetic distance with a large number of haplotypes. Further epidemiological studies are needed to understand its genetic variability. No sub-populations have been recognized in P. westermani based on the presented molecular data.

Predicting carrying capacity of a large carnivore from prey densities: a new approach

Background

Large carnivores play a crucial role in maintaining the balance of the ecosystem. Successful conservation initiatives have often led to a huge increase in predators which has often led to negative interactions with humans. Without the knowledge of the carrying capacity of the top predator, such decisions become challenging. Here, we have derived a new equation to estimate the carrying capacity of tigers based on the individual prey species density.

Methods

We used tiger densities and respective prey densities of different protected areas. Relative prey abundance was used instead of absolute prey density as this could be a better surrogate of the prey preference. We used a regression approach to derive the species-wise equation. We have also scaled these coefficients accordingly to control the variation in the standard error (heteroscedasticity) of the tiger density. Furthermore, we have extended this regression equation for different species to different weight classes for more generalized application of the method.

Results

The new equations performed considerably better compared to the earlier existing carrying capacity equations. Incorporating the species-wise approach in the equation also reflected the preference of the prey species for the tiger. This is the first carrying capacity equation where the individual prey densities are used to estimate the carnivore population density. The coefficient estimates of the model with the comparison with prey-predator power laws also reflect the differential effect of tigers on different prey species. The carrying capacity estimates will aid in a better understanding of the predator-prey interaction and will advance better management of the top predator.