Seroprevalence of Leptospira spp., Toxoplasma gondii, and Dirofilaria immitis in Free-Roaming Cats in Iowa

Seroprevalence and risk factors for Toxoplasma gondii exposure in Australian feral and stray cats using an in-house modified agglutination test

Toxoplasma gondii is a globally distributed zoonotic protist, capable of infecting all warm-blooded animals. In Australia, cats (Felis catus) are the only definitive host capable of spreading T. gondii infection via oocysts. Free-roaming cats are widespread in Australia and can play a central role in the ecology of T. gondii. Therefore, understanding the epidemiology of this parasite in stray and feral cats is essential to understanding the potential risk of infection in animals and humans. Due to a lack of easily accessible commercial kits, an in-house modified agglutination test (MAT) was established to test for IgG antibodies against T. gondii, using cell culture-derived T. gondii tachyzoites, and compared with a commercial MAT. A total of 552 serum samples collected during 2018 - 2021 from stray (n = 456) and feral cats (n = 90) (samples with missing data n = 6) from four Australian states, representing different age groups of both sexes, were screened for antibodies against T. gondii. Risk factors for T. gondii infection were assessed using multivariable logistic regression analysis. The in-house MAT had excellent agreement with the commercial MAT and provided a reliable and economical serological tool for T. gondii screening in animals. The overall observed seroprevalence for T. gondii in cats was 40.4 % (223/552). Bodyweight (as a proxy for age), geographical location, season and whether cats were feral or stray, were factors associated with T. gondii seropositivity in cats. Sex was not found to be a risk factor for T. gondii infection in feral and stray cats. This study shows that Australian stray and feral cats have a high T. gondii seroprevalence, which may translate to significant health impacts for wildlife species, livestock and the public.

Feline leptospirosis prevalence worldwide: A systematic review and meta-analysis of diagnostic approaches

Background and Aim

Leptospirosis in felids (domestic and wild cats) presents an ongoing challenge in our understanding. Numerous studies have reported the detection of Leptospira spp. in these feline populations, highlighting their potential as zoonotic carriers. This systematic review and meta-analysis aimed to provide insight into the global prevalence of leptospirosis in domestic and wild cats.

Materials and Methods

We conducted extensive searches across five databases (PubMed, Scopus, Web of Science, Science Direct, and Google Scholar) following the Preferred Reporting Items for Systematic Reviews and Meta-analyses Protocols guidelines. Random-effect meta-analyses were performed using R software version 4.3.0 to estimate pooled prevalence rates. Subgroup meta-analyses were conducted based on continents, diagnostic methods, sample types, and wildcat genera.

Results

A total of 71 articles on leptospirosis in domestic cats and 23 articles on leptospirosis in wild cats met the eligibility criteria. Our findings indicated a significantly higher pooled seroprevalence of leptospirosis in domestic cats compared with infection prevalence (9.95% [95% confidence interval (CI), 7.60%-12.54%] vs. 4.62% [95% CI, 2.10%-7.83%], p = 0.01). In contrast, no significant difference was observed in pooled seroprevalence and infection prevalence among wild cats (13.38% [95% CI, 6.25%-21.93%] vs. 2.9% [95% CI, 0.00%-18.91%], p = 0.21). A subgroup meta-analysis of domestic cats revealed significant differences in seroprevalence across continents, sample types, and diagnostic methods. On the contrary, wild cats had no significant differences in any of the subgroups.

Conclusion

Leptospira spp. have evidently been exposed to both domestic and wild cats, highlighting their potential roles as reservoir hosts for leptospirosis. These findings highlight the importance of considering felids as a possible public health threat.

A nationwide serological survey for Dirofilaria immitis in companion cats in the United States of America: 3.5% antibody and 0.3% antigen positivity

BACKGROUND

Feline heartworm disease (HWD) is a complex and often misdiagnosed disease in cats, caused by the filarial nematode Dirofilaria immitis. Despite its significant impact, studies reporting the prevalence of D. immitis in apparently healthy pet cats in the USA are lacking.

METHODS

To investigate feline heartworm seroprevalence in apparently healthy pet cats in the USA, serum samples (n = 2165) collected from cats across 47 states and Washington District of Columbia were analyzed for D. immitis antibody (Heska Corp.) and antigen (DiroCHEK®; Zoetis Inc.) with and without acid treatment of the samples.

RESULTS

Antibodies to D. immitis antibodies were identified in 3.5% (76/2165) of cats from 26 states, with a significantly higher prevalence in cats from the westernmost US states (West region; 5.4%, 23/429) compared to those from the South (3.8%, 32/847), Midwest (2.7%, 9/338) and Northeast regions (2.2%, 12/551) (P < 0.04). Antigen from D. immitis was detected in 0.3% (6/2165) of cats, which was significantly lower than the antibody detection (P < 10-4), and no samples were positive for both antibody and antigen.

CONCLUSIONS

This is the largest antibody-based, nationwide serosurvey of feline heartworm in an apparently healthy cat population, and the results suggest that cats in the USA have a high risk of exposure to D. immitis-infected mosquitoes. The high nationwide prevalence (3.5%) indicates that the true prevalence of cats infected with D. immitis in the USA may be significantly underestimated. Our findings emphasize the need for increased awareness and routine testing of cats for heartworm infection, especially in non-endemic areas of the USA. Clinicians should consider appropriate use of broad-spectrum veterinary-approved parasiticides and lifestyle management in feline patients to reduce the risk of infection. Future studies should focus on evaluating the D. immitis infection status in healthy cats and developing better diagnostic assays to detect this complex infection.

Evaluation of Leptospira infection and exposure in free-roaming cat populations in northern California and southern Texas

OBJECTIVES

Leptospirosis is a re-emergent zoonotic bacterial disease associated with renal and hepatic injury. In free-roaming cats in some regions, a high prevalence of Leptospira antibodies has been identified, and pathogenic leptospires have been detected in renal tissue, indicating that they may play a role in Leptospira epidemiology. The objective of this study was to determine the prevalence of Leptospira seroreactivity and urinary shedding of Leptospira DNA in free-roaming cats from northern California and southern Texas. A secondary objective was to compare the results of a point-of-care (POC) assay, designed to detect Leptospira antibodies, with the results of the microscopic agglutination test (MAT) when applied to serum samples from feral cats.

METHODS

Specimens were obtained from free-roaming cats from northern California (n = 52; 2020) and southern Texas (n = 75; 2017). Leptospira quantitative PCR was performed on blood and urine specimens from Californian cats. Serum samples from Californian and Texan cats were subjected to MAT to categorize them as Leptospira antibody-positive or antibody-negative. The performance of the POC assay was assessed using the MAT as the gold standard.

RESULTS

Leptospira DNA was not detected in the blood or urine of any cats tested. The results of the MAT were positive in 17.3% (n = 9) of Californian cats and 10.7% (n = 8) of Texan cats (P = 0.3). The median MAT titer was 1:100 (range 1:100-1:200) in Californian cats and 1:200 (range 1:100-1:800) in Texan cats. The POC assay was negative in all specimens.

CONCLUSIONS AND RELEVANCE

Free-roaming cats in California and Texas are exposed to Leptospira species and may have the potential to act as sentinel hosts. No cats had evidence of current infection, as determined using PCR on blood and urine specimens. The POC test did not reliably detect anti-Leptospira antibodies in these cats. The role of cats in the maintenance or shedding of pathogenic leptospires requires further investigation.

Nationwide molecular survey of Dirofilaria immitis and Dirofilaria repens in companion dogs and cats, United States of America

Background

Heartworms, Dirofilaria immitis, are known to be widespread in dogs and cats in the USA, but there have been no country-wide prevalence studies performed to date. There have also been no large-scale studies to determine whether the closely related species, Dirofilaria repens, occurs in the USA.

Methods

To provide this large-scale data, we examined whole blood samples (n = 2334) submitted from around the USA to the Molecular Diagnostic Laboratory at Auburn University between 2016 and 2022. Quantitative PCRs for D. immitis (targeting 16S rRNA) and D. repens (targeting cytochrome c oxidase subunit 1 gene) were performed to determine the presence of Dirofilaria DNA. DNA sequencing was performed to confirm the results.

Results

Dirofilaria immitis DNA was found in 6.3% (68/1080) of the dogs from 17/39 states, and 0.3% (4/1254) of the cats from 4/42 states. None of the dogs or cats were positive for D. repens. The average 16S rRNA copy number of D. immitis in the dogs was 1,809,604 in 200 µl whole blood, while only a single copy was found in each of the four D. immitis-positive cats. The prevalence of D. immitis in dogs of different ages, sexes, and breeds did not differ significantly, but the prevalence in Southern states (7.5%, 60/803) was significantly higher than in the Western (1.7%, 1/58), Midwest (3.3%, 4/120), and Northeastern states (3.1%, 3/98) (P < 0.05). Dogs positive for D. immitis were identified in each study year (2016: 4.2%, 2/48; 2017: 9.8%, 4/41; 2018: 5.1%, 8/156; 2019: 4.9%, 15/306; 2020: 9.8%, 26/265; 2021: 4.9%, 13/264). Interestingly, dogs infected with Hepatozoon spp. (11.8%, 37/313) were significantly more likely to also be positive for D. immitis than dogs without evidence of Hepatozoon infection (3.9%, 30/760) (P < 0.0001).

Conclusions

To our knowledge, this is the first nationwide molecular survey of Dirofilaria spp. in dogs and cats in the USA, and the largest molecular survey of canine and feline dirofilariosis worldwide. Further studies are warranted to combine PCR with standard heartworm diagnostics to better understand the prevalence of Dirofilaria spp. and aid in determining the risks posed to dogs and cats in the USA.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05459-5.

Leptospira spp. Prevalence in Cats from Southern Italy with Evaluation of Risk Factors for Exposure and Clinical Findings in Infected Cats

Leptospirosis is a worldwide zoonotic disease, but feline leptospirosis is rarely reported. This study aimed at investigating Leptospira spp. prevalence in cats from southern Italy, evaluating risk factors, clinical findings and laboratory data associated with infection. The serum of 112 cats was investigated by microscopic agglutination test (MAT), detecting anti-Leptospira antibodies against 14 pathogenic serovars. Blood and urine samples were tested by a real-time polymerase chain reaction targeting the lipL32 gene of pathogenic Leptospira. Antibodies against serovars Poi, Bratislava, Arborea, Ballum, Pomona and Lora were detected in 15.3% (17/111) of cats (titers range: 20-320). Leptospira spp. DNA was found in 3% (4/109) of blood and 9% (10/111) of urine samples. The spring season was the only risk factor for urinary Leptospira DNA shedding. Laboratory abnormalities significantly associated and/or correlated with Leptospira spp. positivity were anemia, monocytosis, neutrophilia, eosinopenia, increased alanine aminotransferase activity, hypoalbuminemia and hyperglobulinemia. In the investigated areas, cats are frequently infected by Leptospira spp. and can represent an additional reservoir or sentinel for a risk of infection. Moreover, some laboratory changes could be compatible with a pathogenic effect of Leptospira spp. in the feline host.

Prevalence of selected pathogens in ectoparasites from free-roaming domestic cats in the southern Great Plains of the United States

Rickettsia sp. and Bartonella sp. were detected in ectoparasites of free-roaming domestic cats (Felis catus) from a trap-neuter-release program in central Oklahoma during January and February 2020. We used polymerase chain reaction and sequencing to identify fleas containing DNA of five different pathogens: Rickettsia felis (84%), 'Candidatus R. andeanae' (8%), Bartonella henselae (32%), Bartonella clarridgeiae (36%), and Bartonella sp. (8%). Co-infections with R. felis with three Bartonella species were identified. One tick was positive for R. felis, one flea was positive for 'Candidatus R. andeanae' and one ear mite was positive for a Bartonella species. These results highlight the need for more focus on free-roaming domestic cats and their ectoparasites in the Great Plains region.

Serologic and urinary survey of exposure to Leptospira species in a feral cat population of Prince Edward Island, Canada

OBJECTIVES

Recent studies show that cats could play an important role in the transmission of Leptospira species. There are few reports of leptospirosis on Prince Edward Island (PEI) and none in cats. The objective of this study was to determine the prevalence of serum antibodies against Leptospira serovars and of Leptospira DNA in the urine of a population of free-roaming cats.

METHODS

Paired blood and urine samples were collected from 200 cats brought to a trap-neuter-return program. Antibody titers against six Leptospira serovars (Bratislava, Canicola, Gryppotyphosa, Hardjo, Pomona, Icterohaemorrhagiae) were determined by microscopic agglutination test. PCR was performed on urine samples to identify urine shedding of Leptospira DNA.

RESULTS

Antibodies were detected in 20/200 cats (10%) for at least one serovar, with titers ranging from 1:50 to 1:6400 (all serovars tested, except Hardjo). Urine samples of 7/200 cats (3.5%) were PCR-positive.

CONCLUSIONS AND RELEVANCE

Feral cats in PEI had a higher than expected exposure to leptospirosis and can shed DNA from pathogenic Leptospira species in urine. Further studies are needed to determine the prevalence of exposure to leptospirosis in other species on PEI and the potential role of feral cats in transmission of the disease.

Diagnosis and molecular typing of Enterocytozoon bieneusi: the significant role of domestic animals in transmission of human microsporidiosis

Enterocytozoon bieneusi is an obligate intracellular fungus-like parasite with high genetic diversity among mammalian and avian hosts. Based on polymorphism analysis of the ribosomal internal transcribed spacer (ITS), nearly 500 genotypes were identified within E. bieneusi. Those genotypes form several genetic groups that exhibit phenotypic differences in host specificity and zoonotic potential and probably have varying public health implications. Some of the genotypes in Group 1 (e.g., D, EbpC, and Type IV) and Group 2 (e.g., BEB4, BEB6, I, and J) are the most common ones that infect a variety of hosts including humans and thus are of public health importance. By contrast, those genotypes in other genetic groups (Groups 3-11) are mostly restricted to the hosts from which they were originally isolated, which would have unknown or limited impacts on public health. Advances on diagnosis and molecular typing of E. bieneusi are introduced in this review. Genotype distribution pattern of E. bieneusi in major domestic animal groups (pigs, cattle, sheep, goats, cats, and dogs), the role of those animals in zoonotic transmission of microsporidiosis, and food and water as potential vehicles for transmission are interpreted here as well. This review highlights the importance of including more genetic or epidemiological data obtained in the same geographical areas and using more reliable genetic markers to analyze the actual extent of host specificity in E. bieneusi, for the purpose of fully appreciating zoonotic risks of those domestic animals in close contacts with men and enhancing our understanding of the modes of transmission.

Infection with Toxoplasma gondii increases the risk of psychiatric disorders in Taiwan: a nationwide population-based cohort study

This study aimed to evaluate associations between toxoplasmosis and psychiatric disorders in Taiwan based on the National Health Insurance Research Database, Taiwan (1997-2013). Patients newly diagnosed with toxoplasmosis formed the case group (n = 259), and the control group included propensity-score matched patients without toxoplasmosis (n = 1036). The primary outcome was incidence of psychiatric disorders. Cox proportional hazards regression and stratified analyses were performed to examine risk of developing specific psychiatric disorders between patients with and without toxoplasmosis. Patients with toxoplasmosis had significantly higher incidence of psychiatric disorders than those without toxoplasmosis (P = 0.016). A significant difference was found in numbers of psychiatric disorders between the two groups during 14 years of follow-up (log-rank P < 0.001). Those with toxoplasmosis had significantly higher risk of bipolar disorder [adjusted hazard ratio (aHR = 3.60, 95% confidence interval (CI) = 2.07, 7.26), depression (aHR = 4.94, 95% CI = 2.15, 11.80) and anxiety (aHR = 5.36, 95% CI = 2.98, 25.88), but no significant between-group differences were found for schizophrenia and other psychiatric disorders. In conclusion, the present nationwide population-based analysis revealed that Toxoplasma gondii infection in Taiwan significantly increases the risk for developing bipolar disorder, depression and anxiety, but not for schizophrenia and other psychiatric disorders.

All about toxoplasmosis in cats: the last decade

Toxoplasma gondii infections are common in humans and animals worldwide. Toxoplasmosis continues to be of public health concern. Cats (domestic and wild felids) are the most important host in the epidemiology of toxoplasmosis because they are the only species that can excrete the environmentally resistant oocysts in feces. Cats can excrete millions of oocysts and a single cat can spread infection to many hosts. The present paper summarizes information on prevalence, persistence of infection, clinical signs, and diagnosis of T. gondii infections in domestic and wild cats for the past decade. Special emphasis is paid to genetic diversity of T. gondii isolates from cats. Review of literature indicates that a unique genotype (ToxoDB genotype #9 or Chinese 1) is widely prevalent in cats in China and it has been epidemiologically linked to outbreaks of clinical toxoplasmosis in pigs and deaths in humans in China; this genotype has rarely been detected in other countries. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

Leptospira spp. in Cats in Estonia: Seroprevalence and Risk Factors for Seropositivity

Leptospirosis is a zoonotic bacterial disease that affects humans and animals worldwide. Recently, more attention has been paid to Leptospira spp. infections in domestic cats. In this seroepidemiological study, we estimated the prevalence of anti-Leptospira spp. antibodies in domestic cats in Estonia and evaluated risk factors for the seropositivity. A total of 546 surplus feline plasma and serum samples, collected in collaboration with small animal clinics and an animal shelter in 2013 and 2015, were included in this study. The samples were tested for antibodies against Leptospira spp. using a microscopic agglutination test. The panel included Leptospira interrogans serovars Pomona, Icterohaemorrhagiae, Bratislava, Canicola, and Hardjo, and Leptospira kirschneri serovar Grippotyphosa. Titers ≥100 (positive reactions at dilutions ≥1/100) were considered positive. Anti-Leptospira spp. antibodies were detected in 12.8% of the cats. The percentage of cats that tested positive for antibodies against L. interrogans serovars Pomona, Icterohaemorrhagiae, Bratislava, Canicola, and Hardjo were 9.3%, 3.5%, 2.4%, 0.4%, and 0.2%, respectively, and the percentage of cats that tested positive for antibodies against L. kirschneri serovar Grippotyphosa was 7.3%. Of the seropositive cats, 46.5%, 35.2%, 12.7%, 4.2%, and 1.4% tested positive for 1, 2, 3, 4, and 5 serovars, respectively. The prevalence of anti-Leptospira spp. antibodies was 11.2% in pet cats and 16.3% in shelter cats. Among pet cats, the seroprevalence was over four times higher in cats that had access to the outdoors (17.2%) than in indoor cats (3.9%). Multivariable models, one based on data on pet cats only and another including also data on shelter cats, identified having access to the outdoors, being a shelter cat, and being from Western Estonia as the risk factors for seropositivity. Cats could be better protected from exposure to Leptospira spp. by not allowing them to roam freely outdoors.

Leptospirosis in cats: Current literature review to guide diagnosis and management

GLOBAL IMPORTANCE

Leptospirosis is the most widespread zoonosis worldwide. Mammals (eg, rats, horses, cows, pigs, dogs, cats and aquatic species, such as sea lions and northern elephant seals) can all be infected by leptospires. Infection in animals occurs through contact with urine or water contaminated with the bacteria. In people, the disease is acquired mainly from animal sources or through recreational activities in contaminated water.

PRACTICAL RELEVANCE

Literature on the clinical presentation of leptospirosis in cats is scarce, although it has been demonstrated that cats are susceptible to infection and are capable of developing antibodies. The prevalence of antileptospiral antibodies in cats varies from 4% to 33.3% depending on the geographical location. Urinary shedding of leptospires in naturally infected cats has been reported, with a prevalence of up to 68%. Infection in cats has been associated with the consumption of infected prey, especially rodents. Thus, outdoor cats have a higher risk of becoming infected.

CLINICAL CHALLENGES

Clinical presentation of this disease in cats is rare and it is not known what role cats have in the transmission of leptospirosis. Ongoing work is needed to characterise feline leptospirosis.

AUDIENCE

This review is aimed at all veterinarians, both general practitioners who deal with cats on a daily basis in private practice, as well as feline practitioners, since both groups face the challenge of diagnosing and treating infectious and zoonotic diseases.

EVIDENCE BASE

The current literature on leptospirosis in cats is reviewed. To date, few case reports have been published in the field, and information has mostly been extrapolated from infections in people and dogs. This review is expected to serve as a guide for the diagnosis and management of the disease in cats.

EVIDENCE OF LEPTOSPIRA SEROVARS IN WILDLIFE AND LEPTOSPIRAL DNA IN WATER SOURCES IN A NATURAL AREA IN EAST-CENTRAL ILLINOIS, USA

We identified seven Leptospira serovars in wildlife and the presence of leptospiral DNA in water sources at a natural area within a fragmented habitat in Illinois, US. These serovars have been implicated in domestic animal and human leptospirosis, a reemerging zoonotic disease, whose reservoirs include wildlife and domestic animals. We live trapped medium-sized mammals (n=351) near building (H-sites) or forest sites (F-sites). Using serology, we evaluated exposure to Leptospira (L. interrogans serovars Autumnalis, Bratislava, Canicola, Icterohaemorrhagiae, Pomona; L. kirschneri serovar Grippotyphosa; L. borgpetersenii serovar Hardjo). Using PCR, we tested for the presence of leptospires in eight water samples (ponds, creeks, and rainwater runoff) collected near trapping sites. We identified antibody titers in raccoons (Procyon lotor; 121/221) and Virginia opossums (Didelphis virginiana; 60/112), but not in feral cats (Felis catus; 0/18). We found significant differences in overall Leptospira seroprevalence between years (P=0.043) and animal's age in 2008 (P=0.005) and 2009 (P=0.003). Serovars Autumnalis, Bratislava, and Grippotyphosa showed significant differences among age groups with the highest seroprevalence in adults. Females had a higher seroprevalence for Icterohaemorragiae in 2008 (P=0.003) and Hardjo in 2009 (P=0.041). Risk of exposure to Leptospira was higher at F-sites compared to H-sites (odds ratio 2.3, 95% confidence interval 1.3-3.9, P=0.002). We captured more animals with titers >1:800 at H-sites, but there was no association between titer levels and capture site. Six of eight water sources were Leptospira-positive; however, there was no correlation between trapping locations of seropositive animals and positive water sources. Natural areas create opportunities for interspecies interactions, favoring leptospires transmission across species. Understanding that Leptospira serovars are present in natural areas is an integral part of the safe human and pet recreational use of these areas. Our study should raise awareness and build on public education designed to prevent disease transmission between species.