The epidemiology of visceral leishmaniasis in Teresina, Piaui State, Brazil, with special emphasis on diagnosis and transmissibility of canine infection.

Visceral leishmaniasis (VL) is endemic in the semi-arid region of north-eastern Brazil. The causative agent is Leishmania chagasi (infantum). The domestic, peri-domestic and anthropophilic sandfly vector is Lutzomyia longipalpis. The domestic dog may be the principal reservoir of infection in endemic urban regions. The primary aim of this project was to study comparative diagnosis and transmissibility of natural and experimental canine VL in the city of T eresina, Piaui state, Brazil. Most (67 %) of human cases of VL in Teresina occurred in children under 5 years of age, adult VL predominated in males, and there was a seasonal increase in incidence of cases. No phenotypic diversity was found between L. chagasi isolates from dogs and humans, although limited comparisons were performed. Clinical diagnosis, parasitological diagnosis and serology were compared in a cohort of 209 dogs, comprised of both symptomatic and asymptomatic animals. Presence of clinical symptoms was not sufficiently sensitive to diagnose canine VL: only 42 % of dogs positive by reference standard criteria (RS positive) were symptomatic. Parasitology was less sensitive than serology for the diagnosis of canine VL and no parasitological test sho~ed more than 60 % sensitivity in comparison with RS criteria. The indirect fluorescent antibody test (IF A T) and DOT -enzyme linked imrnunosorbent assay (DOT -ELISA) were the most sensitive of the serological assays tested. The direct agglutination test (OAT) was highly specific but lacked sensitivity. Serum samples were more sensitive than filter paper blood spot samples. The Lmet2 DNA probe was generally less sensitive than traditional parasitological and serological methods for diagnosis of canine VL, although the probe was useful for screening sandflies for L. chagasi infections (below). The chance of demonstrating parasites in canine VL increased with the serological titre. Nevertheless, parasitoIogicalIy positive dogs could be found among those that were serologically negative. Large numbers of Lu. longipalpis were found in pigsties and chicken houses in the city of Teresina. The Lmet2 probe was shown to be effective for determining prevalence rates of L. chagasi infection in wild caught sandflies. Prevalence of natural infection in sandflies was particularly high when flies were caught in kennels where there were dogs with disseminated cutaneous infections. Experimental studies demonstrated that Lu. longipaJpis could be very readily infected with L. chagasi by feeding on dogs with canine VL and that transmissibility was associated with amastigote infection of the skin. Altered skin of symptomatic dogs was more infective than normal skin of symptomatic animals. Although symptomatic animals were more infective than asymptomatic animals, asymptomatic dogs with normal skin were still infective to large numbers of sandflies and asymptomatic dogs cannot, therefore, be excluded as a significant reservoir of infection. Transmission of experimental canine VL was demonstrated by a single infective sandfly bite. In a cohort of 25 experimental animals many dogs developed discrete, self-curing, cutaneous lesions, typical of cutaneous leishmaniasis. Seroconversion was the most sensitive test for canine VL, but seronegativity was not a reliable indicator of the absence of infection. Bone marrow positivity was only seen in dogs that were serologically positive. Apparent recovery from L. chagasi infection was seen, with serological reversIOn. Aminosidine, dependent on dose, duration of treatment and clinical status of the infected animal, was shown to be capable of producing clinical recovery and clinical cure in a small proportion of infected dogs, but could not be recommended as a systematic method of control. Single applications of ultra-low volume pyrethroid insecticide to individual animal pens was not effective for controlling Lu. iongipaipis. Nevertheless, pyrethroid insecticides had a high residual activity against Lu. iongipalpis when sprayed on to the walls of animal enclosures. Lambda cyhalothrine (ICON) was the most effective of three pyrethroid insecticides tested in the laboratory against Lu. iongipalpis. Overall, this project has produced unique observations on canine VL, supports the fundamental role of the dog as a reservoir host, and explains why culling of seropositive dogs is likely to have limited impact as a disease control strategy

Efectos de la aplicación postcosecha de silicio en el control de las principales enfermedades de cereza var. Bing

Durante postcosecha de cereza se incrementa la susceptibilidad a patógenos como Alternaria alternata, Botrytis cinerea, Cladosporium herbarum y Penicillium expansum, ocasionando pérdidas significativas. El uso de fungicidas es la estrategia de manejo más empleada, sin embargo, nuevas exigencias de calidad e inocuidad ambiental y alimentaria requieren de la exploración de nuevas alternativas. El silicio, es un mineral cada vez más estudiado en la agricultura por su potencial en el control de patógenos. El objetivo de este trabajo fue determinar el efecto de la aplicación de un formulado comercial de silicato de potasio (K4(SiO4), frente a los principales agentes causales de podredumbres postcosecha en cerezas Bing. Se emplearon frutos recien cosechados, de tamaño homogéneo sin enfermedades ni daños. Los frutos presentaban una firmeza de 72,02 unidades Durofel, 25,47°Brix, 3,79 de pH y una acidez titulable de 1,75 gr de ácido málico/100 mL de jugo. Los tratamientos (T) fueron: To (control, agua), T1 (K4(SiO4), 0.05 L/hL) y T2 (fludioxonil 0.22 L/hL, Scholar®). Se determinaron dos efectos: i) curativo (EC), con la realización de heridas, inoculación del patógeno, incubación (3 horas), y posterior tratamiento; y, ii) preventivo (EP), con realización de heridas, tratamiento y finalmente inoculación con el patógeno. Los tratamientos se realizaron por inmersión (15 frutos/3 repeticiones) durante 1 minuto. Las heridas se realizaron en la zona ecuatorial con un elemento punzante (3mm x 3mm) e inocularon con 10 µL de una suspensión de 1x104 conidios/mL de cada patógeno. Los frutos fueron incubados en bolsas, durante 7 días a 20°C - 70% HR. Se determinó la incidencia (%I) y severidad (mm de lesión) por cada patógeno. El análisis estadístico se realizó con RStudio 2023.03.0. En el I% no hubo diferencias en el efecto preventivo y curativo; sin embargo, sí presentaron diferencias significativas T1 y T2 respecto al T0 para todos los patógenos, con similares porcentajes de control. En el efecto preventivo, T1 fue más eficaz en el control de C. herbarum que T2, mientras que éste último lo fue para B. cinerea. En la severidad, T2 mostró diferencias significativas con respecto a T0 y T1 en B. cinerea y P. expansum. Si bien se necesitan más estudios, estos resultados preliminares muestran la actividad antifúngica del K4(SiO4) in vivo en cereza frente a los principales patógenos de heridas, e indicarían que la aplicación postcosecha, sería una interesante alternativa como sustituto del fungicida de síntesis química frecuentemente utilizado.Facultad de Ciencias Agrarias y Forestale

Experimental infection with Leishmania (Viannia) braziliensis, and Leishmania (Leishmania) amazonensis in the marmoset, Callithrix penicillata (Primates: Callithricidae)

Foureen marmosets (Callithrix penicillata) were inoculated intradermally with promastigotes and/or amastigotes of Leishmania (Viannia) brazilensis (L. (V) b.) strains MHOM/BR/83/LTB-300MHOM/BR/85/LTB-12 MHOM/BR/81/LTB-179 and MHOM/BR/82/LTB-250. The evolution of subsequent lesions was studied for 15 to 75 weeks post-inoculation (PI). All but of the L. (V) b. injected marmosets developed a cutaneous lesion at the point of inoculation after 3 to 9 weeks, characterized by the appearance of subcutaneous nodules containing parasites. parasites were isolated by culture (Difco Blood Agar) from all 11 positive animals. The maximum size of the lesions was variable and ranged between 37 mm² to 107 mm². Ulceration of primary nodules became evident after 3 to 12 weeks in all infected marmosets, but was faster and larger in 5 of the 11 animals. The active lesions persisted in 9 out of 11 Callithrix until the en of the observation period, which varied from 15-75 weeks. In 3 animals spontaneous healing of their lesions (13 to 25 weeks, PI) was observed buth with cryptic parasitism. In another 2 infected animals there was regression followed by reactivation of the cutaneous lesions. The appearance of smaller satellite lesions adjacent to primary ones, as well as metastatic lesions to the ear lobes, were documented in 2 animals. Promastigotes of L. (Leishmania) amazonensis (L.(L)a.) MHOM/BR/77/LTB-16 were inoculated in 1 marmoset. This animal remained chronically infected for 6 months and the lesions developed in a similar manner to L.(V)b. infected marmosets. No significant differences in clinical and parasitological behaviour were observed between promastigote or amastigote derived infections of the 2 species. Both produced chronic, long lasting lesions which eventually healed. The same was true for parameters of size and ulceration. Skin tests converted to parasite in 11 of 15 inected masmosets and in 10 of 12 parasite positive animnals. Moderate levels of circulating antibodies were also observed by IFAT /IgG assays. In spite of the failure to reproduce the mucosal form of the disease, an important aspect of the Callithrix model in experimental cutaneous leishmaniasis lies in the reproduction of 2 clinical events that are common in humans, namely, the chronic ulceration and spontaneous healing of the lesions