Canine leishmaniasis in the Rif mountains (Moroccan Mediterranean coast): a seroepidemiological survey

A sero-epidemiological survey has been conducted in several localities of the province of Nador to investigate canine leishmaniasis in the North-Eastern slope of the Rif mountains (Mediterranean coast of Morocco). Serum samples collected from 257 dogs were analysed using indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA) to detect anti-Leishmania infantum antibodies. Forty eight (18.7%) of the screened dogs were IFAT positive and 54 (21.0%) were ELISA positive; the concordance of the two methods was 96.1%. The prevalence of infection is significantly higher in dogs more than four years of age whereas no significant difference in prevalence of infection was seen between males and females. The frequent symptoms observed in seropositive dogs were the enlargement of lymph nodes (57.4%), emaciation (51.9%) and skin involvement (25.9%). However, 38.9% of those dogs showed no one of the major symptoms of visceral leishmaniasis. Leishmania isolated from three of the examined dogs was identified as L. infantum MON-1. These results show that the North-Eastern slope of the Rif mountains is one of the most active Mediterranean areas of visceral leishmaniasis and confirm that the dog is the main reservoir of L. infantum.     

The infection risk of visceral leishmaniasis among household members of active patients

Human visceral leishmaniasis (HVL), caused by Leishmania infantum is mainly observed as sporadic cases in Turkey and dogs are considered as the main reservoir of the disease. The incidence of visceral leishmaniasis among members of households where a HVL infection has already been diagnosed was studied in clusters around the diagnosed cases in different regions in Turkey. A total of 47 serum samples collected from the households of 11 proven visceral leishmaniasis patients were screened for anti-Leishmania antibodies by indirect immunofluorescent antibody test (IFAT). Three and one such household members belonging to the different families were found to be seropositive and borderline, respectively. Diagnosis was confirmed with the presence of amastigotes in bone marrow aspiration samples in all seropositives while the borderline case with slight and indefinitive symptoms of VL was followed only serologically at 3-month intervals and improved spontaneously in 1 year. Household members of individuals with previously confirmed visceral leishmaniasis were found to have higher frequency of the disease suggesting the household members should be included in the risk group for visceral leishmaniasis and serological screening should be performed for the detection of possible infection.     

Passive case detection for canine visceral leishmaniasis control in urban Brazil: Determinants of population uptake

BackgroundIn Brazil, the transmission of Leishmania infantum in urban settings is closely related to infection among dogs, with occasional transmission to humans. Serological screening of dogs for Leishmania spp. infection on requests of their owners (passive case detection) represents a frequent, but little studied, practice within the scope of Brazilian public health. This study identified factors associated with canine visceral leishmaniasis (CVL) diagnosis-seeking behavior of dog owners in Rondonópolis (236,000 inhabitants), a municipality in Central-Western Brazil where VL is endemic. Also, we evaluated the profile of dog owners and their animals screened on free demand.Methodology/Principal findingsUsing mixed effects negative binomial regression, we modelled the number of dogs screened for Leishmania infection on free demand per neighborhood from 2011 to 2016 as a function of time-dependent predictors (current or recent canine seropositivity and human VL incidence), distance to the screening site, and demographic variables. We assessed potential delays in the effect of time-dependent predictors on the outcome. Among 12,536 dogs screened for Leishmania infection, 64.2% were tested during serosurveys and 35.8% were tested on free demand. Of these, 63.9% were positive. Uptake of screening under free demand was strongly associated with higher levels of canine seropositivity in the neighborhood (current or recent) and decreasing distance to the screening site. A subsample of dog owners (n = 93) who sought CVL screening between 2016 and 2017 were interviewed in more detail. Owners with better socioeconomic status and dogs with apparent CVL clinical manifestations prevailed among them.Conclusions/SignificanceTo support timely CVL management, passive case detection along with awareness activities aimed at dog owners should be encouraged in endemic areas. Screening sites should be prioritized in accessible zones, as well as in socio-economically disadvantage areas. In parallel, CVL active case detection should be continued as a surveillance tool to guide control actions.     

Prevalence and Risk Factors for Echinococcal Infection in a Rural Area of Northern Chile: A Household-Based Cross-Sectional Study

Background

Hydatidosis is a zoonotic disease of worldwide distribution caused by Echinococcus granulosus. Our study aimed to determine the prevalence of human and canine echinococcosis as well as the associated risk factors in a rural area of the Limarí province in northern Chile.

Methodology/Principal Findings

A cross-sectional study was conducted between August and November 2009 using a stratified sampling design in each of the five districts of the province. In the selected villages, up to 10 households were sampled. Serum and fecal samples from an adult family member and a dog were collected from each participating household. Risk factors were assessed by standardized questionnaires. Seroprevalence was assessed using a multi-step approach: an ELISA for screening, IFA, IHA and western blot for confirmation of results, respectively. The prevalence of echinococcal infection in dogs was determined by coproantigen genus specific ELISA. Chi-square, Fisher tests and logistic regressions were used to assess risk factors for human seropositivity and dog copropositivity. A seroprevalence of 2.6% (10/403) and coproprevalence of 28% (26/93) was recorded for humans and dogs respectively. Contact with dogs and dog feces were risk factors for human seropositivity while dog copropositivity was associated with home slaughter of livestock (OR = 3.35; CI 90%: 1.16–6.85) and households de-worming dogs (OR = 2.82; CI 90%: 1.33–8.43).

Conclusions/Significance

Echinococcal infection of humans and their dogs is common in Limarí province. Risk factors for human seropositivity were related to contact with domestic dogs and their feces, whereas those for dogs were home slaughter of livestock and the practice of de-worming dogs.     

Prevalence and factors associated with Leishmania infantum infection of dogs from an urban area of Brazil as identified by molecular methods

Background

Various factors contribute to the urbanization of the visceral leishmaniasis (VL), including the difficulties of implementing control measures relating to the domestic reservoir. The aim of this study was to determine the prevalence of canine visceral leishmaniasis in an urban endemic area in Brazil and the factors associated with Leishmania infantum infection among seronegative and PCR-positive dogs.

Methodology

A cross-sectional study was conducted in Belo Horizonte, Minas Gerais, Brazil. Blood samples were collected from 1,443 dogs. Serology was carried out by using two enzyme-linked immunosorbent assays (Biomanguinhos/FIOCRUZ/RJ and “in house”), and molecular methods were developed, including PCR-RFLP. To identify the factors associated with early stages of infection, only seronegative (n = 1,213) animals were evaluated. These animals were divided into two groups: PCR-positive (n = 296) and PCR-negative (n = 917) for L. infantum DNA. A comparison of these two groups of dogs taking into consideration the characteristics of the animals and their owners was performed. A mixed logistic regression model was used to identify factors associated with L. infantum infection.

Principal Findings

Of the 1,443 dogs examined, 230 (15.9%) were seropositive in at least one ELISA, whereas PCR-RFLP revealed that 356 animals (24.7%) were positive for L. infantum DNA. Results indicated that the associated factors with infection were family incomeConclusionsPCR detected a high prevalence of L. infantum infection in dogs in an area under the Control Program of VL intervention. Socioeconomic variables, dog behavior and the knowledge of the owner regarding the vector were factors associated with canine visceral leishmaniasis (CVL). The absence of previous serological examination conducted by the control program was also associated with L. infantum infection. It is necessary to identify the risk factors associated with CVL to understand the expansion and urbanization of VL.     

Risk of Infection with Leishmania spp. in the Canine Population in the Netherlands

The dog is the main reservoir of Leishmania infantum, the causative agent of visceral leishmaniasis (VL) in humans in Southern Europe. In order to identify the risk of dogs from a Leishmania non-endemic area traveling to a Leishmania -endemic area becoming infected and the risk of transmitting infection to humans in non-endemic areas an investigation was performed, in which the results of a questionnaire were combined with the results of a serologic survey.     

Factors influencing ocelot occupancy in Brazilian Atlantic Forest reserves

Over 80% of Atlantic Forest remnants are <50 ha and protected areas are embedded in a matrix dominated by human activities, undermining the long‐term persistence of carnivores. The ocelot (Leopardus pardalis) is an opportunistic species, but little is known about its tolerance to habitat alterations and the influence of other species on its occupancy in Atlantic Forest remnants. We used camera traps to assess ocelot occupancy in protected areas of Atlantic Forest in southeastern Brazil. We found a positive correlation between the occupancy of ocelots and top predators (jaguars, Panthera onca, and pumas, Puma concolor), and a weaker negative effect between the number of domestic dogs (Canis familiaris) detected and ocelot occupancy. Ocelot detection was higher at sites with more eucalyptus, suggesting that ocelots frequently use these areas. Better‐protected areas surrounded by permeable matrices may be critical to the persistence of ocelots in the fragmented Atlantic Forest.     

Leishmania (Viannia) braziliensis: epidemiology of canine cutaneous leishmaniasis in the State of Paraná (Brazil)

The present study examines the role that dogs play in the maintenance of the Leishmania cycle in the State of Paraná, Southern Brazil. Dogs were examined in three regions where cutaneous leishmaniasis is endemic or epidemic (R1-Vale da Ribeira; R2-Central region of Paraná State and R3-Northern region). To determine serum prevalence rates ELISA was used. In regions endemic for Trypanosoma cruzi (R1 and R3), serum from dogs seroreactive towards Leishmania antigen was subjected to T. cruzi adsorption in order to eliminate cross-reaction with common antigen epitopes. Concomitantly, dogs with cutaneous lesions were biopsied to isolate and identify parasites using RAPD. Leishmania were classified by the phenetic method using the Jaccard coefficient of similarity, and grouped by Unweighted Pair-Group Method using an Arithmetic Average (UPGMA). A total of 410 dogs were studied. In R1 (Vale da Ribeira) 159 dogs were evaluated of which 10 had anti-Leishmania antibody. In R2 (Central Paraná), 39 animals were examined of which 8 were seropositive. In R3 (the North) 212 dogs were evaluated of which 39 animals were seropositive. Thirteen dogs had cutaneous lesions and the parasites were isolated from a dog with mucocutaneous lesion in R1, two animals with simple skin lesions in R2 and 10 dogs with multiple lesions in R3. The identification of the parasite by molecular methods showed it to be L. (Viannia) braziliensis. Based on this information, the role of domestic dogs in Leishmania infection of cutaneous leishmaniasis in Paraná is discussed.     

Interpretation of laboratory data during cryptic leishmaniasis in dog

Leishmaniasis is a zoonosis caused by an intracellular parasite belonging to the genus Leishmania. In Europe, Africa, South America and China, visceral leishmaniasis is caused by L. infantum. The vectors of leishmaniasis are phlebotomine sandflies belonging to the genera Phlebotomus. According to the World Health Organization there are 2 million new cases each year and 1/10 of the world's population is at risk of infection. Leishmaniasis is considered a zoonosis and human are generally accidental hosts. The animal reservoir includes rodents, dog and other mammals. Several studies have indicate that half of the dogs with antileishmanial antibodies have no signs of disease although, animal with subclinical infections are potentially infectious to sand flies. The factors determining susceptibility or resistence to visceral leishmaniasis remain unclear, but the genetics of the host may play a major role. Clinical signs are: intermittent fever, hepatosplenomegaly, skin lesions and ulcers, alopecia, onychogryphosis, anemia, thrombocytopenia and hypergammaglobulinemia. In mice, the outcome of infection depends on the polarized activation of one of two subsets of CD4+ T cells, Th1 or Th2, the subdivision into Th1 and Th2 cells is based on the pattern of cytokines that they produce. Th1 cells produce gamma interferon (IFN-gamma) and interleukin -2 (IL-2), whereas Th2 cells produce IL-4, IL-5, and IL-10. An important difference between susceptible and resistant mice is that the resistant mice are able to switch to a Th1 profile and control the disease. An important factor in the "decision" to form a Th1 or Th2 phenotype is the early cytokine environment, and IL-12 is one of the cytokines that contributes significantly to the establishment of the Th1 phenotype. Canine leishmaniosis is endemic in the Mediterranean basin and, in most cases is caused by the parasite Leishmania infantum. The main clinical findings are skin lesions, local or generalized lymphoadenopathy, loss of body weight, glomerulopathy, ocular lesions, epistaxis and lameness. Non pruritic skin lesions are the usual manifestation and several forms have been described, such as exfoliative dermatitis and alopecia, and ulcerative, nodular and pustular dermatitis. Seroepidemiological studies of canine leishmaniasis have revealed a large number of asymptomatic seropositive animals. Moreover in areas where leishmaniasis is highly endemic, high proportion of apparently healthy animals show low levels of anti-Leishmania antibodies. Others have regressive forms of the desease, and their antibody levels will decrease in the following months or years; still others maintain low levels of antibodies without developing the desease for many years. However, the total number of infected animals is unknown. Canine leishmaniasis is a major zoonosic parasitic disease, enzootic in the Mediterranean area, caused by the intracellular protozoan Leishmania infantum. The dog is the main reservoir host of the parasite. However, most infected dogs do not present any clinical signs, and there is evidence that Leishmania infection prevalence rates in areas of endemicity are higher than those ascertained by serological studies. Visceral leishmaniasis is becoming a real problem of public health because it is an opportunistic infection in immunocompromised patients and in human immunodeficiency virus-positive subjects. The detection of the extent of the infection, particularly among asymptomatic dogs, is of great importance for the control of leishmaniasis. PCR has been applied successfully in recent years to detect Leishmania spp. even in the cases with any of the clinical manifestation of leishmaniasis. Very recently, real-time PCR for Leishmania has been applied to evaluate the parasitic load of dog tissues both at the time of the diagnosis and during follow-up of the therapy and to measure cytokine mRNA levels in different clinical samples of infected and uninfected dogs.     

Epidemiologic aspects of an emerging focus of visceral leishmaniasis in Tbilisi, Georgia

Background

Over the last 15 years, visceral leishmaniasis (VL) has emerged as a public health concern in Tbilisi, the capital of Georgia.

Methodology/Principal Findings

Seroepidemiological surveys were conducted to determine the prevalence and incidence of infection in children and dogs within the main focus of VL, and to identify risk factors associated with human infection. Of 4,250 children investigated, 7.3% were positive by direct agglutination test in a baseline survey; an apparent incidence rate of 6.0% was estimated by one year follow-up. None of the seropositive children progressed to VL during the survey. Increased seropositivity at one year was predicted by presence at baseline of clustered flying insects (OR = 1.49; P = 0.001), perceived satisfactory sanitation (OR = 1.65; P<0.001), stray dogs (OR = 1.33; P = 0.023), and by persistent fever during the 6 months prior to baseline survey (OR = 14.2; P<0.001). Overall, 18.2% (107/588) of domestic and 15.3% (110/718) of stray dogs were seropositive by the rk39 dipstick test. Clinical VL signs were found in 1.3% of domestic and 2.9% of stray, seropositive dogs. Parasites isolated from human and dog samples were identified by PCR and phylogenetic analysis of the Leishmania 70 kDa heat-shock protein (HSP70) gene as Leishmania infantum.

Conclusions/Significance

There is an active focus of L. infantum transmission in Tbilisi with a high prevalence of human and canine infections.     

Host preferences of the phlebotomine sandfly Lutzomyia longipalpis in Amazonian Brazil

Experiments were undertaken to determine the relative attractiveness of humans, dogs and chickens to Lutzomyia longipalpis, the principal vector of Leishmania chagasi causing American visceral leishmaniasis. Field experiments in two villages on Marajó Island, Pará State, Brazil, showed that one boy attracted significantly more flies than one dog or chicken, and slightly fewer flies than a group of six chickens. Experiments with laboratory-bred female flies showed that a significantly greater number of flies engorged on a single human than on either a single dog or chicken, and man-biting catches demonstrated the willingness of flies to bite in the field. It appears that Lu.longipalpis has catholic feeding habits, the attractiveness of different hosts being largely a function of their relative sizes. These results are discussed with reference to the epidemiology of visceral leishmaniasis in Brazil.     

Leishmania infection in humans, dogs and sandflies in a visceral leishmaniasis endemic area in Maranhão, Brazil

Leishmania infection in humans, dogs and sandflies was examined in the endemic visceral leishmaniasis (VL) municipality of Raposa, state of Maranh?o, Brazil. In this study, we examined Leishmania chagasi infection in the blood serum of both humans and Canis familiaris and the natural Leishmania sp. infection rate in the sandfly vector, Lutzomyia longipalpis. Enzyme-linked immunosorbent assay, indirect immunofluorescence reaction and polymerase chain reaction were performed to detect Leishmania infections in humans, dogs and sandflies, respectively. Overall, 186 out of 986 studied human beings were infected with L. chagasi parasites, representing an infection prevalence of 18.9%. An even higher infection rate was detected in dogs, where 66 (47.8%) out of 138 were infected. Among all Lu. longipalpis captured (n = 1,881), only 26.7% were females. The Leishmania infection frequency for the vector Lu. longipalpis was 1.56%. Remarkably, all infected sandflies were found in the peridomiciliary area. Furthermore, a high incidence of asymptomatic forms of VL in the human and canine populations was observed. The results of this study suggest autochthonous transmission of L. chagasi in this endemic area for visceral leishmaniasis because infection by Leishmania sp. was identified in all important elements of the transmission chain.     

Are insecticide-impregnated dog collars a feasible alternative to dog culling as a strategy for controlling canine visceral leishmaniasis in Brazil?

In a zoonotic visceral leishmaniasis (ZVL)-endemic area in Brazil, deltamethrin-impregnated collars (DMC) were fitted to 136 dogs for 5 months and significantly reduced the odds of increasing their anti-Leishmania antibody titer during this period by 50% (95% confidence interval 29-87%, P=0.01), as compared with a population of 97 uncollared dogs with pre-intervention prevalence within the same town. Mathematical modeling suggests that under typical Brazilian ZVL-endemic conditions, the epidemiological impact of community-wide DMC application should be greater than the currently practiced dog culling strategy, but that its impact will be dependent on collar coverage and loss rate. Both interventions should have a higher proportional impact in regions of lower endemicity, but the relative advantage of DMC over culling increases with transmission rate. Sensitivity analyses indicate that the impact of either intervention is not significantly affected by variation in the biology of the sandfly vector, but is greatly influenced by variation in dog mortality and serorecovery rates.     

Evaluation of two DNA probes specific for Leishmania infantum in the diagnosis of canine leishmaniasis

This study reports on the evaluation of two L. infantum specific DNA probes for the diagnosis of canine leishmaniasis. The probes presented very satisfying performances in terms of specificity (100%) and predictive value of the positive result (100%). However, their sensitivity (35.3%) and the clinical complexity of canine infections render their use difficult in epidemiological surveys of visceral leishmaniasis aiming at measuring the prevalence of the dog infection by L. infantum. The sensitivity of these tools has improved (66.7%) when dogs presenting patent leishmaniasis were considered. Such probes constitute appropriate tools to confirm suspected cases of leishmaniasis. Unlike the classical parasitological and serological tools, this kind of tools allows a concomitant detection and identification of the causative agent. Therefore, despite their low sensitivity, these probes can still be of importance in epidemiological investigations.     

A serological and epidemiological evaluation of risk factors for toxocariasis in children in central Poland

The level of specific anti-Toxocara IgG was examined in 343 children from central Poland with suspected Toxocara infection. Based on the presence of specific IgG antibodies and clinical signs and symptoms, toxocariasis was confirmed in 249 patients. The serological results of diagnosed cases were analysed in connection with epidemiological data (contamination of soil around the children's homes and presence of a dog or a cat). A higher prevalence of soil contamination with Toxocara eggs was found in suburban and rural areas (30.9% and 24.6%, respectively) whereas it was lower in urban areas (10.3%). In about 40% of the children whose households were not contaminated, a decrease in the antibody level was observed 2 years after treatment for toxocariasis, while there was no such decline in those living in contaminated places. The logistic regression model employed to determine the correlation between seropositivity in the children and selected epidemiological risk factors showed a statistically significant relationship in connection only with dog ownership (P = 0.0238). The present results have demonstrated the high risk of toxocariasis for children from rural and suburban areas in Poland. The sero-epidemiological investigations indicated that re-infection might be the reason for persistence of seropositivity after treatment.     

Canine visceral leishmaniasis caused by Leishmania infantum in Senegal: risk of emergence in humans?

In the context of global warming and the risk of spreading arthropod-borne diseases, the emergence and reemergence of leishmaniasis should not be neglected. In Senegal, over the past few years, cases of canine leishmaniasis have been observed. We aim to improve the understanding of the transmission cycle of this zoonosis, to determine the responsible species and to evaluate the risk for human health. An epidemiological and serological study on canine and human populations in the community of Mont Rolland (Thiès area) was conducted. The data showed a high seroprevalence of canine leishmaniasis (>40%) and more than 30% seropositive people. The dogs’ seroprevalence was confirmed by PCR data (concordance > 0.85, Kappa > 0.7). The statistical analysis showed strong statistical associations between the health status of dogs and seropositivity, the number of positive PCRs, clinical signs and the number of Leishmania isolates. For the first time, the discriminative PCRs performed on canine Leishmania strains clearly evidenced that the pathogenic agent is Leishmania infantum. The results obtained show that transmission of this species is well established in this area. That the high incidence of seropositivity in humans may be a consequence of infection with this species is discussed.     

Sand fly vectors (Diptera, Psychodidae) of American visceral leishmaniasis areas in the Atlantic Forest, State of Espírito Santo, southeastern Brazil

The aim of this study was to evaluate the sand fly fauna of American visceral leishmaniasis (AVL) endemic areas within the Central Atlantic Forest Biodiversity Corridor, State of Espírito Santo, southeastern Brazil. The sand fly captures were performed between January, 1989 and December, 2003 in localities where autochthonous cases of AVL were recorded, as well as in their boundary areas. Sand flies were collected from surrounding houses and domestic animal shelters using two to five CDC automatic light traps, and manual captures were also performed using mouth aspirators in one illuminated Shannon trap during the first four hours of the night. We used cladistic analysis to determine the geographic relationships among the collected sand fly species as well as the index species for the occurrence of other sand flies. A total of 62,469 sand flies belonging to 17 species and eight genera was collected in 164 localities from nine municipalities with AVL records. The richness (S=17) and diversity (H=0.971) of sand flies were lower than in conservation areas and similar to modified environments in the Atlantic Forest of Espírito Santo. Lutzomyia longipalpis was identified in 79 localities. The cladistic analysis identified Evandromyia lenti as the index species for Lutzomyia longipalpis. The latter seems to be the main vector of AVL in the Central Atlantic Forest Biodiversity Corridor due to its high abundance and distribution matching the disease occurrence. Therefore, Evandromyia lenti may be used as an index species for the occurrence of Lutzomyia longipalpis.     

Prevalence of seropositivity to pathogens in small carnivores in adjacent areas of Lazovskii Reserve

The prevalence of infectious diseases in wild and feral carnivores is poorly known in Primorsky Krai, where rare species such as the Amur tiger and the Far East leopard roam. In this study we evaluated the prevalence of seropositivity in feral (cats, dogs) and wild (raccoon dog, badger, American mink, Far Eastern wild cat) carnivores to various pathogens: distemper virus, parvovirus, feline immunodeficiency and feline leukemia virus, feline coronavirus, Toxoplasma gondii, Mycoplasma sp., and Chlamydia sp. It was shown that seropositivity occurred significantly more frequent in feral animals than in wild ones. The highest percentage of seropositive animals was observed in feral dogs. It is these diseases that can be dangerous for the Amur tiger and the Far East leopard, thus affecting their populations.     

Contrasting patterns in the small-scale heterogeneity of human helminth infections in urban and rural environments in Brazil

Marked heterogeneity exists in the patterns of parasitic infection between individuals, households and communities. Analysis of parasite distributions within populations is complicated by the fact that parasite distributions are highly aggregated and few studies have explicitly incorporated this distribution when investigating small-scale spatial heterogeneities. This study aimed to quantify the small-scale (within- and between-household) heterogeneity of helminth infection in an area of Minas Gerais State, Brazil, with rural and urban sectors. Parasitological data from a cross-sectional survey of 1,249 individuals aged 0-86 years from 242 households were analysed. Within-household clustering of infection was assessed using random effect logistic regression models and between-household spatial heterogeneity was assessed using a Bayesian negative binomial spatial model. The overall prevalence of hookworm (Necator americanus) was 66.9%, the prevalence of Schistosoma mansoni was 44.9% and the prevalence of Ascaris lumbricoides was 48.8%. Statistical analysis indicated significant (within) household and (between household) spatial clustering of hookworm in both rural and urban areas and of S. mansoni in rural areas. There was no evidence of either household or spatial clustering of S. mansoni in urban areas. The spatial correlation of S. mansoni was estimated to reduce by half over a distance of 700 m in the rural area. Rural hookworm had a much smaller half-distance (28 m) and urban hookworm showed an even smaller half-distance (12 m). We suggest that such species-specific differences in patterns of infection by environment are primarily due to variation in exposure and parasite life cycle, although host genetic factors cannot be ruled out.     

Evidence for an impact on the incidence of canine leishmaniasis by the mass use of deltamethrin-impregnated dog collars in southern Italy

Dogs are the domestic reservoir of Leishmania infantum Nicolle (Kinetoplastida: Trypanosomatidae), the agent of zoonotic human visceral leishmaniasis. In southern Europe, where canine leishmaniasis (CanL) is widespread due to L. infantum, killing seropositive dogs is considered unacceptable and drug treatment has low efficacy in preventing transmission. We made a field evaluation of the efficacy of deltamethrin dog collars in a CanL focus of southern Italy, Mount Vesuvius area of Campania region, where the vector is Phlebotomus perniciosus Newstead (Diptera: Psychodidae), by assessing their impact on the incidence of CanL in an intervention town, compared to that in dogs of control towns where no collars were fitted. During two consecutive transmission seasons, collars were fitted to 350 (1998) and 354 (1999) dogs from San Sebastiano al Vesuvio (70% of the canine population). Control dogs (371 and 264 in the 2 years, respectively) were from four towns of the same area. Before each transmission season, the CanL seroprevalence in the intervention and control towns was evaluated by cross-sectional surveys and found to be similar (about 15% in 1998 and 10% in 1999, respectively). After each transmission period, incidence rates of seroconversions were determined in adult dogs that were serologically negative before the season under evaluation, and in puppies. After the 1998 season, 2.7% of the dogs in the intervention town seroconverted compared to 5.4% in the control towns (50% protection, P = 0.15). After the 1999 season, 3.5% of collared dogs seroconverted compared to 25.8% of control dogs (86% protection, P < 0.001). The increase in seroconversion rates recorded in control dogs suggests an increase in the Leishmania force of infection in the canine reservoir during the 1999 sandfly season, as supported by the concomitant increase of human cases in control towns and in the whole Campania region. Our results suggest that the impact of mass use of deltamethrin-impregnated dog collars on the incidence of CanL may be negligible during low transmission seasons, or probably in low endemic foci, but can be very strong when the force of transmission is high.