Cutaneous Leishmaniasis in dogs: is high seroprevalence indicative of a reservoir role?

Canine leishmaniasis in the Americas: etiology, distribution, and clinical and zoonotic importance

Canine leishmaniasis is a widespread disease on the American continent, with cases reported from Uruguay to the USA and Canada. While numerous Leishmania spp. have been reported in dogs in this region, Leishmania infantum and Leishmania braziliensis are the most common etiological agents of canine leishmaniasis from a continental perspective. Nonetheless, other species may predominate locally in some countries. The participation of dogs in the transmission cycle of various Leishmania spp. has long been speculated, but evidence indicates that their role as reservoirs of species other than L. infantum is negligible. Various native wildlife (e.g., small rodents, marsupials, sloths, and monkeys) are, in fact, the primary hosts of Leishmania spp. in the Americas. In this review, an updated list of Leishmania spp. infecting dogs in the Americas is presented, along with their distribution and clinical and zoonotic importance.

Trypanosoma cruzi infection in dogs along the US-Mexico border: R0 changes with vector species composition

Infection with Trypanosoma cruzi, etiological agent of Chagas disease, is common in US government working dogs along the US-Mexico border. This 3145 km long border comprises four states: Texas (TX), New Mexico (NM), Arizona (AZ) and California (CA) with diverse ecosystems and several triatomine (a.k.a., kissing bug) species, primary vectors of T. cruzi in this region. The kissing bug (Heteroptera: Reduviidae) community ranging from CA to TX includes Triatoma protracta (Uhler), Triatoma recurva (Stål) and Triatoma rubida (Uhler) and becomes dominated by Triatoma gerstaeckeri Stål in TX. Here, we ask if T. cruzi infection dynamics in dogs varies along this border region, potentially reflecting changes in vector species and their vectorial capacity. Using reversible catalytic models of infection, where seropositivity can be lost, we estimated an R0 (Estimate ± S.E.) of 1.192 ± 0.084 for TX and NM. In contrast, seropositivity decayed to zero as dogs aged in AZ and CA. These results suggest that dogs are likely infected by T. cruzi during their training in western TX, with a force of infection large enough for keeping R0 above 1, i.e., the disease endemically established, in TX and NM. In AZ and CA, a lower force of infection, probably associated with different vector species communities and associated vectorial capacity and/or different lineages of T. cruzi, results in dogs decreasing their seropositivity with age.

First report of imported canine visceral leishmaniasis cases in Panama, Central America: Public health implications

According to the last leishmaniasis report from the Pan American Health Organization (2021) so far Panama is considered free of visceral leishmaniasis (VL). Although the presence of potential vectors and reservoirs involved in the VL transmission cycle have been described in some rural regions of the country, no cases have been reported in humans and domestic or wild animals. Dogs play an important role in the urban transmission of VL; therefore, it is important to detect possible cases of canine visceral leishmaniasis (CVL) in the country. In this sense,this study reports for the first time the Leishmania (Leishmania) infantum infection in imported dogs in Panama. Eleven dogs with clinical suspicion of CVL were evaluated by parasitological (bone marrow aspirate smear), serological (indirect immunofluorescence and/or reference immunochromatographic rapid test) and molecular tests (conventional PCR). The dogs included in this study were analyzed during the period from 2013 to 2020. All dogs presented clinical manifestations compatible with CVL. The samples were initially evaluated by smears and/or rapid serological tests by private practice veterinarians, and later confirmed by serological and/or molecular tests at the national reference laboratory for Leishmania diagnosis. The diagnosis was confirmed in 5/11 dogs by serological, parasitological and/or conventionals PCR targeting kDNA minicircle and Hsp70 gene. Leishmania (L.) infantum species was identified in 3/5 dogs by PCR-RFLP and by sequencing Hsp70-PCR products. This study evidenced the need to increase awareness of private practitioners as well as public health veterinarians on visceral leishmaniasis (VL), and to consider this parasitosis in the differential diagnosis of dogs with clinical and epidemiological characteristics compatible with the disease.

Comparison of Serological and Molecular Assays for Bartonella Species in Dogs with Hemangiosarcoma

Currently, a gold standard diagnostic test for Bartonella infection in dogs is lacking. This represents a critical limitation for the development and evaluation of new diagnostic tests, as well as for the diagnosis of, and research on, bartonellosis in dogs. This retrospective observational study aims to compare the results of commonly performed and newly-reported Bartonella spp. diagnostic tests in banked clinical specimens from 90 dogs with hemangiosarcoma (HSA) using composite reference standard (CRS) and random effects latent class analysis (RE-LCA) techniques. Samples from each dog were tested using six serological or molecular diagnostic assays, including indirect fluorescent antibody (IFA) and Western blot (WB) for the detection of antibodies in serum, and qPCR and droplet digital PCR (ddPCR) in blood and fresh frozen tissue biopsy samples (mainly splenic HSA tumors and histopathologically normal spleen or skin/adipose tissue). Bartonella infection prevalence was estimated to be 78% based on the CRS (parallel testing with all six assays), and 64% based on the RE-LCA model. The assay with the highest diagnostic accuracy was qPCR performed on fresh frozen tissue biopsy samples (sensitivity: 94% by RE-LCA and 80% by CRS; specificity: 100%). When comparing newly-reported to traditional Bartonella diagnostic assays, ddPCR was more sensitive for the detection of Bartonella DNA than qPCR when testing blood samples (36% vs. 0%, p < 0.0001). Dogs that were positive on serological assays alone with negative molecular assays were highly unlikely (<3%) to be classified as infected by the RE-LCA model. These data indicate that Bartonella spp. DNA can be PCR amplified from fresh frozen tissues from a majority of dogs with HSA using both qPCR and ddPCR, supporting the use of these methods for future controlled studies comparing the prevalence of Bartonella spp. DNA in the tissue of dogs with HSA to that of unaffected controls.

Novel High-Throughput Multiplex qPCRs for the Detection of Canine Vector-Borne Pathogens in the Asia-Pacific

The Asia-Pacific hosts a large diversity of canine vector-borne pathogens (VBPs) with some of the most common and most pathogenic, generating significant mortality as well as a spectrum of health impacts on local dog populations. The VBPs Anaplasma platys, Babesia gibsoni, Babesia vogeli, Ehrlichia canis, Hepatozoon canis and haemotropic Mycoplasma spp. are all endemic throughout the region, with many exhibiting shifting geographical distributions that warrant urgent attention. Moreover, many of these species cause similar clinical signs when parasitising canine hosts, whilst knowledge of the exact pathogen is critical to ensure treatment is effective. This is complicated by frequent coinfection that can exacerbate pathology. Here, we describe the development, optimisation and validation of two novel quadruplex Taq-Man based real-time PCRs (qPCRs) for the specific and sensitive detection of the aforementioned VBPs. To ensure accurate evaluation of diagnostic performance, results of our qPCRs were evaluated on field samples from Thai dogs and compared with both conventional PCR (cPCR) results and next-generation sequencing (NGS) metabarcoding. Our qPCRs were found to be more sensitive at detecting canine VBP than cPCR and generated results similar to those achieved by NGS. These qPCRs will provide a valuable high-throughput diagnostic tool available to epidemiologists, researchers and clinicians for the diagnosis of key canine VBPs in the Asia-Pacific and further afield.

Clinical, Molecular and Serological Diagnosis of Canine Leishmaniosis: An Integrated Approach

Canine leishmaniosis (CanL) is caused by protozoans of the genus Leishmania and characterized by a broad spectrum of clinical signs in dogs. Early diagnosis is of great importance in order to perform an appropriate therapy and to prevent progression towards severe disease. The aim of this study was to compare a point-of-care molecular technique, i.e., the loop-mediated isothermal amplification (LAMP), with a real-time polymerase chain reaction (Rt-PCR), and three serological techniques, i.e., immunofluorescence antibody test (IFAT), enzyme-linked immunosorbent assay (ELISA), and a rapid SNAP Leishmania test, to develop an integrated approach for the diagnosis of CanL. Sixty dogs were chosen after physical examination and collection of blood and sera samples, fine-needle aspiration of lymph nodes, and conjunctival swabs were performed. Lymphadenopathy (82.3%), as well as clinicopathological alterations of total proteins (70.6%), were the most frequent signs. Forty-one (68.3%) samples resulted positive at least to one technique. IFAT resulted in the best serological diagnostic method (specificity = 100%, sensitivity = 97.2%), detecting a higher number of positive samples than those revealed by other techniques. Among the samples used for molecular analysis, fine-needle aspiration of lymph nodes was revealed as the best sample source. LAMP showed a substantial agreement (κ = 0.80; p <0.0001) with Rt-PCR; therefore, it could be promising for the rapid diagnosis of CanL. Nevertheless, further studies should be performed to confirm these findings.

Leishmania spp. Infection Rate and Feeding Patterns of Sand Flies (Diptera: Psychodidae) from a Hyperendemic Cutaneous Leishmaniasis Community in Panamá

American cutaneous leishmaniasis (ACL) is a common and important vector-borne parasitic zoonosis in Panamá. Here, we study Leishmania spp. infection rates and blood-feeding patterns among common sand flies in Trinidad de Las Minas, a rural community with hyperendemic ACL transmission, and where a deltamethrin fogging trial was performed. Sand flies were collected from April 2010 to June 2011 with light traps installed inside and in the peridomicile of 24 houses. We restricted our analysis to the most abundant species at the study site: Lutzomyia trapidoi, Lutzomyia gomezi, Lutzomyia panamensis, Lutzomyia triramula, and Lutzomyia dysponeta. We detected Leishmania spp. infection in sand flies by polymerase chain reaction (PCR) amplification of the internal transcribed spacer region 1 (ITS-1) in pooled females (1-10 females per pool). Host species of engorged sand flies were identified using a cytochrome b PCR. From 455 sand fly pools analyzed, 255 pools were positive for Leishmania spp., with an estimated infection rate (confidence interval) of 0.096 [0.080-0.115] before the deltamethrin fogging which slightly, but not significantly (P > 0.05), increased to 0.116 [0.098-0.136] after the deltamethrin fogging. Blood meal analysis suggested that pigs, goats, and birds were the most common sand fly blood sources, followed by humans and domestic dogs. DNA sequencing from a subsample of ITS-1 positive pools suggests that Leishmania panamensis, Leishmania naiffi, and other Leishmania spp. were the parasite species infecting the most common vectors at the study site. Our data confirm an association between sand fly species, humans, domestic dogs, and pigs and Leishmania spp. parasites in rural Panamá.

Exposure to Leishmania spp. infection and Lutzomyia spp. in individuals living in an area endemic for visceral leishmaniasis in Brazil

INTRODUCTION:

This study aimed to investigate human exposure to Leishmania spp. infection and sandflies in an area endemic for the disease.

METHODS:

The presence of antibodies specific for Leishmania spp. and saliva of Lutzomyia spp. and that of L. infantum DNA in blood were evaluated.

RESULTS:

Antibodies against Leishmania spp. and sandfly saliva were observed in 20.8% and 37.7% of individuals, respectively. DNA of Leishmania spp. was amplified from the blood of one patient.

CONCLUSIONS:

The results suggest that Leishmania spp. infection may be underdiagnosed in this area.

Clinical and Pathological Aspects of Canine Cutaneous Leishmaniasis: A Meta-analysis

PURPOSE

In the present study, we described the most prevalent clinical symptoms, the most affected organs, and the macro and microscopic lesions associated with cutaneous leishmaniasis.

METHODS

Two independent researchers performed an extensive systematic review of the literature in four stages (identification, screening, eligibility, and inclusion) to identify studies published between January 2002 and November 2018 from the following electronic databases: Web of Science, PubMed, SciELO, Science Direct, and Google Scholar. Meta-analysis was conducted in "Metaprop" package of R 3.4.2 software.

RESULTS

The electronic search yielded 3896 results, out of which 155 were further analyzed based on the full-text. Data extracted from 16 articles were included in the meta-analysis, representing a total of 430 leishmaniasis cases. Only 43% of all animals were identified to exhibit the clinical and cutaneous changes characteristic of leishmaniasis based on the observation that skin lesions were the most prevalent clinical sign and were present in 86% of all cases. Other less prevalent symptoms included weight loss, cachexia, apathy and lymph node enlargement. Histopathological analysis showed that the skin was the most affected organ, affecting 64% of cases, followed by lymph nodes (12%), spleen (8%) and liver (7%).

CONCLUSIONS

Therefore, our current findings suggest that cutaneous leishmaniasis could lead to visceral disease. Notably, our findings indicated no clinical manifestation patterns in cutaneous leishmaniasis, since the same host species may present different clinical conditions.

A review on the occurrence of companion vector-borne diseases in pet animals in Latin America

Companion vector-borne diseases (CVBDs) are an important threat for pet life, but may also have an impact on human health, due to their often zoonotic character. The importance and awareness of CVBDs continuously increased during the last years. However, information on their occurrence is often limited in several parts of the world, which are often especially affected. Latin America (LATAM), a region with large biodiversity, is one of these regions, where information on CVBDs for pet owners, veterinarians, medical doctors and health workers is often obsolete, limited or non-existent. In the present review, a comprehensive literature search for CVBDs in companion animals (dogs and cats) was performed for several countries in Central America (Belize, Caribbean Islands, Costa Rica, Cuba, Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Puerto Rico) as well as in South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, French Guiana, Guyana (British Guyana), Paraguay, Peru, Suriname, Uruguay, Venezuela) regarding the occurrence of the following parasitic and bacterial diseases: babesiosis, heartworm disease, subcutaneous dirofilariosis, hepatozoonosis, leishmaniosis, trypanosomosis, anaplasmosis, bartonellosis, borreliosis, ehrlichiosis, mycoplasmosis and rickettsiosis. An overview on the specific diseases, followed by a short summary on their occurrence per country is given. Additionally, a tabular listing on positive or non-reported occurrence is presented. None of the countries is completely free from CVBDs. The data presented in the review confirm a wide distribution of the CVBDs in focus in LATAM. This wide occurrence and the fact that most of the CVBDs can have a quite severe clinical outcome and their diagnostic as well as therapeutic options in the region are often difficult to access and to afford, demands a strong call for the prevention of pathogen transmission by the use of ectoparasiticidal and anti-feeding products as well as by performing behavioural changes.

Molecular typing reveals the co-existence of two transmission cycles of American cutaneous leishmaniasis in the Andean Region of Venezuela with Lutzomyia migonei as the vector

BACKGROUND The transmission routes for American cutaneous leishmaniasis (ACL) are in flux, so studies examining its transmission in humans, mammalian hosts, and sand fly vectors are urgently needed. OBJECTIVES The aim of this work was understand the epidemiological cycles of Leishmania spp., which causes ACL in the Andean Region of Venezuela, by identifying the Leishmania and the sand fly species involved in human and dog infections. METHODS Thirty-one biopsies from patients in Mérida and Táchira states with suspected ACL were studied by both parasitological tests (cultures and hamster inoculation) and a molecular test [Internal transcribed spacer 1 (ITS1) nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)]. We also conducted a survey to detect Leishmania infection in dogs (Immunifluorescence antibody test and ITS1 nested PCR-RFLP) and sand flies (ITS1 nested PCR-RFLP) from El Carrizal, a highly endemic focus of ACL in Venezuela. FINDINGS Three different Leishmania species were identified in the clinical samples from humans (Leishmania braziliensis, L. guyanensis, and L. mexicana) and dogs (L. guyanensis and L. mexicana). The predominant sand fly species found were those from the Verrucarum group (infected with L. mexicana) and Lutzomyia migonei (infected with L. guyanensis and L. mexicana). MAIN CONCLUSIONS We show that Lu. migonei may be the putative vector in two ACL epidemiological cycles, involving L. guyanensis and L. mexicana. We also report for the first time the presence of L. guyanensis in domestic animals.

Stray Dog Population in a City of Southern Mexico and Its Impact on the Contamination of Public Areas

To assess the risk of zoonotic pathogen transmission as function of stray dog presence and health status, a cross-sectional study was carried out in a large city of southern Mexico that lacks comprehensive strategies for the control of stray canine populations. The photographic capture-recapture method was used to estimate the density of dogs/km². In the same way, dog feces from 14 public parks of the city were collected to determine the prevalence and intensity of infection with gastrointestinal parasites. The canine population was estimated between 65 and 80 thousand dogs, with a population density of 1,081 dogs/km², mostly males (71.4%). A high proportion of dogs (72.3%) were found to be in good body condition score (BCS 3). The person:dog ratio was 2.3. The likelihood of being in the BCS 2 category was lower in areas with a higher density of dogs. All feces collected from the parks contained eggs of intestinal parasites, most of them with a medium (42.9%) to high (35.7%) infection intensity, notably Ancylostoma caninum. It was recorded that cases with a low-intensity of GI infection showed polyparasitism (35.7%) associated with A. caninum. There is a large population of stray dogs that roam freely in the streets of Campeche city with access to sources of food, which is reflected by their good BCS, and dogs do not have access to preventive medicine programs (de-worming) and thus contaminate public parks with feces with significant parasitic egg loads of zoonotic importance.

Enzootic mosquito vector species at equine encephalitis transmission foci in the República de Panamá

The identification of mosquito vector species present at arboviral enzootic transmission foci is important to understand transmission eco-epidemiology and to propose and implement prevention and control strategies that reduce vector-borne equine encephalitis transmission. The goal of this study was to identify mosquito species potentially involved in the transmission of enzootic equine encephalitis, in relation to their abundance and diversity at three endemic regions in the República de Panamá. We sampled adult mosquitoes during the dry and rainy season of Panamá. We employed CDC light traps with octanol, EV traps with CO₂ and Trinidad 17 traps baited with live hamsters. Traps were deployed in the peridomicile and extradomicile of houses from 18:00 to 6:00 h. We estimated the abundance and diversity of sampled species. We collected a total of 4868 mosquitoes, belonging to 45 species and 11 genera, over 216 sampling nights. Culex (Melanoconion) pedroi, a major Venezuelan equine encephalitis vector was relatively rare (< 2.0% of all sampled mosquitoes). We also found Cx. (Mel) adamesi, Cx. (Mel) crybda, Cx. (Mel) ocossa, Cx. (Mel) spissipes, Cx. (Mel) taeniopus, Cx. (Mel) vomerifer, Aedes scapularis, Ae. angustivittatus, Coquillettidia venezuelensis, Cx. nigripalpus, Cx. declarator, Mansonia titillans, M. pseudotitillans and Psorophora ferox all species known to be vectorially competent for the transmission of arboviruses. Abundance and diversity of mosquitoes in the sampled locations was high, when compared with similar surveys in temperate areas. Information from previous reports about vectorial competence / capacity of the sampled mosquito species suggest that sampled locations have all the elements to support enzootic outbreaks of Venezuelan and Eastern equine encephalitides.

Molecular and serological investigation of Trypanosoma cruzi infection in dogs in French Guiana

Clinical cases of Chagas disease, an infection caused by the parasite Trypanosoma cruzi, have been recently described in humans and dogs in French Guiana, a French overseas department located in South America. Elsewhere in endemic countries for this disease, cases of asymptomatic infections have been described. We performed a prevalence survey of the infection in dogs in Cayenne and Kourou, the main cities of French Guiana. In 2014 and 2016, blood samples were taken from 153 dogs from Cayenne and Kourou. All dogs were apparently healthy at the time of sampling. Sex and age of the dogs were recorded as well as the location where they lived. Serum samples from dogs were screened using a rapid immunochromatographic test (Chagas Stat-Pak®Assay, Chembio, USA) detecting anti-T. cruzi antibodies. Simultaneously, a real-time PCR targeting T. cruzi kDNA was performed on the blood samples of the dog. Six dogs (3.9%) were positive only in serology and one (0.6%) only in qPCR. Two dogs were positive for both tests. The prevalence of infection (positivity for one of the two tests) was 5.8% (9/153). There was no significant difference (χ² test) between Cayenne (5/100) and Kourou (4/53), between males (3/60) and females (6/93), or between 2014 (2/55) and 2016 (7/98). Canine surveillance is a useful tool for the public health risk assessment of Chagas disease. Positive dogs, even when asymptomatic, should be treated as they can serve as a reservoir for T. cruzi.

Molecular and serological detection of Trypanosoma cruzi in dogs (Canis lupus familiaris) suggests potential transmission risk in areas of recent acute Chagas disease outbreaks in Colombia

Chagas disease is a zoonotic infection widely distributed in tropical and subtropical regions of America, including more than 50% of the Colombian territory. In the last years, an increase of outbreaks of acute Chagas disease has been observed in the east of the country due to environmental changes and mammal movements toward human settlements. Given the importance of dogs (Canis lupus familiaris) as reservoir hosts and sentinels of Trypanosoma cruzi infection across different regions of America, in this study we reported a serological and molecular detection of T. cruzi infection in 242 dogs from an endemic area of Meta department (East of Colombia), with recent emergence of acute Chagas disease outbreaks. The distribution of T. cruzi infection in dogs was not homogeneous, ranging from 0-41.4% and 0-5.1% in different sampling sectors, through serological (ELISA/IFAT) and molecular methods (conventional and real time PCR), respectively. Statistical analysis indicated that dog infection was associated with specific sampling sectors. Our results show a moderate seroprevalence of infection and active circulation of T. cruzi in dogs from this zone, which suggest areas with potential risk of infection to human that must be taken into consideration when Chagas disease control programs need to be implemented.

Risk factors associated with Trypanosoma cruzi exposure in domestic dogs from a rural community in Panama

Chagas disease, caused by Trypanosoma cruzi infection, is a zoonosis of humans, wild and domestic mammals, including dogs. In Panama, the main T. cruzi vector is Rhodnius pallescens, a triatomine bug whose main natural habitat is the royal palm, Attalea butyracea. In this paper, we present results from three T. cruzi serological tests (immunochromatographic dipstick, indirect immunofluorescence and ELISA) performed in 51 dogs from 24 houses in Trinidad de Las Minas, western Panama. We found that nine dogs were seropositive (17.6% prevalence). Dogs were 1.6 times more likely to become T. cruzi seropositive with each year of age and 11.6 times if royal palms where present in the peridomiciliary area of the dog's household or its two nearest neighbours. Mouse-baited-adhesive traps were employed to evaluate 12 peridomestic royal palms. All palms were found infested with R. pallescens with an average of 25.50 triatomines captured per palm. Of 35 adult bugs analysed, 88.6% showed protozoa flagellates in their intestinal contents. In addition, dogs were five times more likely to be infected by the presence of an additional domestic animal species in the dog's peridomiciliary environment. Our results suggest that interventions focused on royal palms might reduce the exposure to T. cruzi infection.

Macroecological patterns of American Cutaneous Leishmaniasis transmission across the health areas of Panamá (1980-2012)

American Cutaneous Leishmaniasis (ACL) is a neglected vector-borne zoonosis that persists despite increasing socio-economic development and urbanization in Panamá. Here, we investigate the association between environmental changes and spatio-temporal ACL transmission in the Republic of Panamá (1980-2012). We employ a macroecological approach, where patterns of variation in ACL incidence at the spatially coarse-grained scale of health areas are studied considering factors linked to the ecology of ACL transmission. We specifically study impacts of climatic variability, measured by the different phases of El Niño Southern Oscillation (ENSO), within diverse ecosystems and sand fly (Diptera: Psychodidae) vector species, as well as heterogeneous local climatic patterns, deforestation, population growth rates, and changes in social marginalization. We found that over the study period, patterns of ACL incidence: (i) were asynchronous with clusters changing from east to west of the Panamá Canal, (ii) trends increased in the west, and decreased or remained nearly constant in the east, independent of human population growth, (iii) generally increased in years following El Niño, and (iv) decreased as forest cover increased. We found no significant association between changes in socio-economic indicators and ACL transmission. Regarding vector abundance and presence, we found that studies had been biased to locations east of the Panamá canal, and that, in general, the abundance of dominant vector species decreased during the cold phase of ENSO. Finally, our results indicate that a macroecological approach is useful to understand heterogeneities related to environmental change impacts on ACL transmission.