ARCHITECT Chagas® as a single test candidate for Chagas disease diagnosis: evaluation of two algorithms implemented in a non-endemic setting (Barcelona, Spain).

OBJECTIVES: To evaluate two algorithms for the diagnosis of chronic and congenital Chagas disease (CD), both including the chemiluminescent microparticle immunoassay ARCHITECT Chagas® (CMIA) as a single test but with an amended signal-to-cut-off ratio (S/CO) of ≥6, instead of an S/CO of ≥1 as indicated by the manufacturer. METHODS: The study encompassed two panels of retrospective samples: 831 sera from 786 adolescents and adults (panel A), and 96 sera from 35 newborn infants with CD-infected mothers (panel B). A CMIA-negative result was deemed conclusive, whereas samples with an S/CO ≥ 0.8 were confirmed by a second test (BioELISA Chagas, ELISAr). RESULTS: In panel A, seropositivity was 13% (102/786); 10 samples gave discordant results for CMIA and ELISAr, all of which were CMIA positive and had CD confirmed through a previous diagnosis by two positive serological tests. In panel B, all newborns were considered non-infected based on both a progressive decrease in antibody titres over time and negative real-time PCR results. CMIA still gave positive results in two infants aged 10 months but no S/CO values ≥6 were observed from 4 months on. CONCLUSIONS: CMIA is a firm candidate for use as a single CD diagnostic test in non-endemic countries. The algorithm with the ≥6 S/CO is as an efficient method for chronic CD diagnosis. CMIA could also be used as a single test to screen infants for congenital infection at the age of 10 months or even earlier if applying the corrected cut-off ratio, although further studies are required.

Evaluation of canine leishmaniosis vaccine CaniLeish® under field conditions in native dog populations from an endemic Mediterranean area-A randomized controlled trial.

Dog vaccination is considered an effective way of reducing Leishmania infantum infection incidence in the canine population, as well as its transmission to humans. However, the use of partially effective vaccines can have the detrimental effect of "masking" vaccinated asymptomatic carriers, capable of harbouring the parasite and transmitting it to naïve individuals. After eight years on the European market, few studies have been released on CaniLeish® vaccine safety and efficacy. The present study, a one-year randomized CaniLeish® vaccine field trial, was performed in a canine leishmaniosis endemic area and included animals selected from a native dog population (n = 168). No severe adverse reactions were observed in vaccinated dogs (n = 85). Cases of active L. infantum infection were detected by serological, molecular and clinical follow-up of dogs. One-year post-vaccination, no differences in number or severity of L. infantum active infections were observed between study groups (n = 4 in each group). Vaccine-induced cellular immunity, assessed through interferon-γ quantification, showed significantly higher levels of this cytokine one-month post-vaccination in the vaccine group (p < 0.001), but no differences were observed after nine months between trial groups (p = 0.078). These results fail to support the reported CaniLeish® efficacy in the prevention of active L. infantum infection in dogs from endemic areas and naturally exposed to the parasite.

Seroprevalence of canine Leishmania infantum infection in the Mediterranean region and identification of risk factors: The example of North-Eastern and Pyrenean areas of Spain.

The Mediterranean basin is an endemic region for canine leishmaniosis (CanL), where it represents a major veterinary problem and raises human health concerns. However, the distribution of the disease is heterogeneous and not all countries and locations have been equally studied and characterized. This work describes the situation of CanL in Girona province (Catalonia, Spain), for which no data has been previously reported, and presents a relevant study to exemplify other areas with similar characteristics across the region. Four cross-sectional seroprevalence surveys were performed from 2012 to 2016 throughout the province, including 36 sampling stations in 26 localities and a total of 593 dogs. For each animal, individual and location variables were also collected. Additionally, each dog owner answered a questionnaire about their knowledge of CanL and preventive methods used. Blood samples were analysed by an in-house ELISA and a mixed logistic regression model was used to assess the relationship between pre-determined variables and dog seropositivity. A Spearman's correlation was used to assess the association between dog owners' perceived risk of CanL and Leishmania infantum seropositivity in dogs at a given location. The overall true seroprevalence estimated for Girona province was 19.5% (95%CI: 15.5-23.5), of which only 6.8% (10/146) were considered symptomatic. Age of the dog [OR = 1.21 (95%CI: 1.11-1.31); p < 0.001] and altitude [OR = 0.02 (95%CI: 0.001-0.19); p = 0.001] were identified as risk factors for the infection. The results obtained in this study are expected to aid in the implementation of directed control programmes in CanL endemic areas throughout Europe, as well as to provide suitable data for the design of better risk assessment maps of the disease.