Seroprevalence of antibodies against Leishmania spp among dogs in the United States

Phylogenetic climatic niche conservatism in sandflies (Diptera: Phlebotominae) and their relatives

Phylogenetic niche conservatism is a pattern in which closely related species are more similar than distant relatives in their niche-related traits. Species in the family Psychodidae show notable diversity in climatic niche, and present an opportunity to test for phylogenetic niche conservatism, which is as yet rarely studied in insects. Some species (in the subfamily Phlebotominae) transmit Leishmania parasites, responsible for the disease leishmaniasis, and their geographic range has been systematically characterized. Psychodid genus ranges can be solely tropical, confined to the temperate zones, or span both. We obtained observation site data, and associated climate data, for 234 psychodid species to understand which aspects of climate most closely predict distribution. Temperature and seasonality are strong determinants of species occurrence within the clade. Next, we built a phylogeny of Psychodidae, and found a positive relationship between pairwise genetic distance and climate niche differentiation, which indicates strong niche conservatism. This result is also supported by strong phylogenetic signals of metrics of climate differentiation. Finally, we used ancestral trait reconstruction to infer the tropicality (i.e., proportion of latitudinal range in the tropics minus the proportion of the latitudinal range in temperate areas) of ancestral species, and counted transitions to and from tropicality states. We find that tropical and temperate species produced almost entirely tropical and temperate descendant species, respectively. Taken together, our results imply that climate niches in psychodids are strongly predicted by phylogeny, and represent a formal test of a key prediction of phylogenetic niche conservatism in a clade with implications for human health.

Leishmaniasis in the United States: Emerging Issues in a Region of Low Endemicity

Leishmaniasis, a chronic and persistent intracellular protozoal infection caused by many different species within the genus Leishmania, is an unfamiliar disease to most North American providers. Clinical presentations may include asymptomatic and symptomatic visceral leishmaniasis (so-called Kala-azar), as well as cutaneous or mucosal disease. Although cutaneous leishmaniasis (caused by Leishmania mexicana in the United States) is endemic in some southwest states, other causes for concern include reactivation of imported visceral leishmaniasis remotely in time from the initial infection, and the possible long-term complications of chronic inflammation from asymptomatic infection. Climate change, the identification of competent vectors and reservoirs, a highly mobile populace, significant population groups with proven exposure history, HIV, and widespread use of immunosuppressive medications and organ transplant all create the potential for increased frequency of leishmaniasis in the U.S. Together, these factors could contribute to leishmaniasis emerging as a health threat in the U.S., including the possibility of sustained autochthonous spread of newly introduced visceral disease. We summarize recent data examining the epidemiology and major risk factors for acquisition of cutaneous and visceral leishmaniasis, with a special focus on implications for the United States, as well as discuss key emerging issues affecting the management of visceral leishmaniasis.

Demographics and travel history of imported and autochthonous cases of leishmaniosis in dogs in the United States and Canada, 2006 to 2019

BACKGROUND

Leishmania infantum infections are reported in foxhounds throughout the United States (US) and Canada, but only rarely in other dog breeds. A seroprevalence report from 2006 documented leishmaniosis in foxhounds (8.9%) tested in the US between 2000 and 2003. All other breeds were seronegative.

OBJECTIVE

To reexamine demographics and travel history of L. infantum-infected dogs in the US and Canada, we hypothesize detection of L. infantum in more foxhounds than nonfoxhounds and that infected nonfoxhounds will have traveled to endemic regions.

ANIMALS

A total of 125 dogs positive for L. infantum by immunofluorescent antibody, PCR, or both.

METHODS

Retrospective, descriptive study of L. infantum-infected dogs between 4 January 2006 and 22 May 2019. Travel history and known lineage to foxhounds was collected from questionnaires.

RESULTS

Leishmania infantum was detected in 125 (6.4%) of 1961 dogs tested between 4 January 2006 and 22 May 2019, of which 10 (8%) were foxhounds and 115 (92%) were nonfoxhound breeds. Travel history available for 69 (55%) dogs showed 60 (86.9%) dogs had traveled outside of the US or Canada. Nine (13%) dogs had not traveled outside of the US or Canada, 5 of which were nonfoxhounds.

CONCLUSIONS AND CLINICAL IMPORTANCE

The majority of L. infantum cases were detected in nonfoxhounds, many of which had traveled to L. infantum-endemic countries, and several nonfoxhound breeds had no travel history. Leishmania surveillance should be considered for dogs that return from L. infantum-endemic regions to monitor emergence of this zoonotic disease in the US and Canada.

Update on Canine and Feline Blood Donor Screening for Blood-Borne Pathogens

An update on the 2005 American College of Veterinary Internal Medicine (ACVIM) Consensus Statement on blood donor infectious disease screening was presented at the 2015 ACVIM Forum in Indianapolis, Indiana, followed by panel and audience discussion. The updated consensus statement is presented below. The consensus statement aims to provide guidance on appropriate blood‐borne pathogen testing for canine and feline blood donors in North America.

Successful treatment of canine cutaneous leishmaniasis using radio-frequency induced heat (RFH) therapy

Canine cutaneous leishmaniasis (CCL) is a significant veterinary problem. Infected dogs also serve as parasite reservoirs and contribute to human transmission of cutaneous leishmaniasis (CL). Current treatments for CCL are cumbersome and toxic because they are prolonged and involve multiple injections of antimonials. Radio-frequency induced heat (RFH) therapy has been found to be highly effective against CL in humans. Here, we examined the efficacy of topical RFH therapy in the treatment of CL in two pet dogs. We found that RFH therapy induced complete clinical cure and lesion healing within 45 days and both dogs have remained disease free for the last 16 months. This report is the first to demonstrate that a single topical application of RFH therapy is safe and effective in inducing long-term cure of CCL.

Factors associated with Trypanosoma cruzi exposure among domestic canines in Tennessee

Trypanosoma cruzi , the etiologic agent of Chagas' disease, is enzootic in animal populations of the southeastern United States. In the United States, T. cruzi prevalence has been reported for over 20 different wildlife species, and 7 autochthonous human cases have been documented since 1955. Previous canine (Canis familiaris) serosurveys have been limited either by small sample size or confined geographic reporting areas. In this study, we report a seroprevalence of 6.4% among 860 canines from 31 counties and 5 ecoregions throughout Tennessee, using an indirect immunofluorescent assay (IFA). Statistically significant associations between seropositivity and age, weight, and outdoor living were noted. Differences in seropositivity were not seen based on American Kennel Club (AKC) group, sex, habitat, land cover, and ecoregion. Greater attention should be given to possible T. cruzi transmission in Tennessee and veterinarians should consider Chagas' disease as a differential diagnosis with compatible signs.

Infections in immunocompetent and immune-deficient mice with promastigotes of a North American isolate of Leishmania infantum

Leishmania infantum, an etiologic agent of zoonotic visceral leishmaniasis, is widespread among foxhounds in the United States. Experimental infections with a North American isolate of L. infantum were evaluated using two inoculation routes in immunocompetent and immunosuppressed mouse strains. Groups of 2-5 interferon gamma gene knockout (IFN-gamma-KO) (BALB/c-Ifng), inducible nitric oxide synthase (NOS) gene knockout (iNOS-KO) (C57BL/6), B-cell-deficient (microMT) (C57BL/6), and BALB/c mice were intravenously (i.v.) or subcutaneously (s.c.) inoculated with various doses of promastigotes of the LIVT-1 strain of L. infantum. None of the mice developed clinical signs of leishmaniasis during the 8-9 weeks of the study. Promastigotes were cultured from spleens of all i.v.-infected mice by 3 days post culture. Spleens from s.c.-infected mice inoculated with greater than 1 x 10(6) parasites became culture positive 3-24 days post culture, but promastigotes were not cultured from mice infected with 1 x 10(5) or 5 x 10(5) LIVT-1 promastigotes. Histological lesions were prominent in the livers of i.v.-infected mice but were mild to nonexistent in s.c. infection. Serological responses were low and transient determined by indirect fluorescent antibody testing in all groups. These results indicate that the i.v. route of infection is superior to the s.c. route in a mouse model of North American leishmaniasis and that mice lacking INF-gamma, iNOS or mice that are B-cell-deficient are not more susceptible to acute infection.

Canine and feline blood donor screening for infectious disease

Consensus Statements of the American College of Veterinary Internal Medicine (ACVIM) provide veterinarians with guidelines regarding the pathophysiology, diagnosis, or treatment of animal diseases. The foundation of the Consensus Statement is evidence‐based medicine, but if such evidence is conflicting or lacking, the panel provides interpretive recommendations on the basis of their collective expertise. The Consensus Statement is intended to be a guide for veterinarians, but it is not a statement of standard of care or a substitute for clinical judgment. Topics of statements and panel members to draft the statements are selected by the Board of Regents with input from the general membership. A draft prepared and input from Diplomates is solicited at the Forum and via the ACVIM Web site and incorporated in a final version. This Consensus Statement was approved by the Board of Regents of the ACVIM before publication.