Trabajos publicados en la Revista Agronomía Mesoamericana 1990-2021

El objetivo de este documento es orientar a los interesados en acceder a las publicaciones de la revista Agronomía Mesoamericana, desde su primer volumen y número, efectuado en 1990 y ubicadas en el Portal de Revistas Académicas de la Universidad de Costa Rica https://revistas.ucr.ac.cr/index.php/agromeso/issue/archiveUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM

Detección y caracterización molecular de Cryptosporidium spp. en terneros de lechería de la provincia de Valdivia, Chile

Objective: To detect acid-fast oocysts of Cryptosporidium spp. using the Ziehl-Neelsen stain (ZN) and apply molecular tools with the 18S rARN and 60 kDa glycoprotein (gp60) genes to characterize the species and subtypes present in the Valdivia province. Material and methods: 275 samples of calves from 15 dairy farms located in the Valdivia province were analyzed by ZN stain. Samples that were positive to ZN were then submitted to PCR processing aiming as target the 18S rARN and gp60 genes, with subsequent sequencing of the latter. Results: Thirty samples were positive to ZN, of which 46.6% (14/30) were confirmed by PCR amplification for 18S rARN and from those, 42.8% (6/14) also amplified the gp60 target using PCR. Subsequent sequencing of this gene showed the presence of C. parvum in 100% of the isolates and the subtypes IIaA15G2R1 (3/6), IIaA14G1R1 (2/6) and IIaA17G1R1 (1/6). Conclusions: Subtype IIaA15G2R1 was predominant, being found in two boroughs of the province. The subtype IIaA14G1R1 was found in two farms located in the same borough and, to our knowledge, this is the first time that this subtype has ever been reported in cattle in both Chile and the continent. Finally, subtype IIaA17G2R1 has been found sporadically in calves just like in the present study.Objetivo: Detectar ooquistes ácido-alcohol resistentes de Cryptosporidium spp. en terneros mediante tinción Ziehl-Neelsen (ZN) y caracterizar molecularmente las especies y subtipos presentes en la provincia de Valdivia, a través del uso de herramientas moleculares con los genes 18S rARN y gp60 que codifica una glicoproteína de 60 kDa. Materiales y métodos: 275 muestras de heces de terneros pertenecientes a 15 predios lecheros de la provincia de Valdivia, fueron analizadas mediante tinción de ZN. Las muestras positivas a ZN, se analizaron por PCR mediante la amplificación de una región de los genes 18S rARN y gp60, con posterior secuenciación. Resultados: 30 muestras resultaron positivas a ZN, de las cuales el 46.6% (14/30) logró ser confirmado mediante PCR para 18S rARN y de estas, el 42.8% (6/14) fueron positivas a la PCR para gp60. La secuenciación arrojó la presencia de C. parvum en el 100% de las muestras y los subtipos IIaA15G2R1 (3/6), IIaA14G1R1 (2/6) y IIaA17G1R1 (1/6). Conclusiones: El subtipo IIaA15G2R1 predominó, encontrándose en dos comunas de la provincia. El subtipo IIaA14G1R1 fue encontrado en dos predios de una misma comuna y su hallazgo es el primero en bovinos en Chile y el continente. Finalmente, el subtipo IIaA17G2R1 ha sido encontrado esporádicamente en terneros, al igual que en esta investigación. Las tres variantes han sido reportadas en humanos, sin embargo, no hay registros de estudios que caractericen los subtipos de C. parvum en sistemas de crianza de terneros y trabajadores simultáneamente en Chile, por consiguiente, se debe indagar en el tema

An epidemiological investigation of Coxiella burnetii and Chlamydia spp. as infectious agents causing abortion in dairy cattle in Uruguay

Infectious diseases are the leading aetiological cause of bovine abortion globally as well as in Uruguayan dairy farms. Studies conducted in this country showed that a proportion of aborted fetuses without diagnosis present histological lesions compatible with the action of an infectious agent. These undiagnosed abortion cases could be due to infectious agents not currently included in the battery of diagnostic tests routinely applied. Infectious agents such as Coxiella burnetii and Chlamydia spp., typically considered to have a minor or relative marginal role in causing abortion in cattle, have never been systematically investigated in Uruguay. This thesis challenged the current diagnostic protocols, seeking evidence supporting the inclusion of these agents to dismiss the number of undiagnosed cases. This work investigated the association of these pathogens with cattle abortion in commercial dairy herds and the potential as zoonotic threats in the local context. The thesis will first introduce the main characteristics of dairy production in Uruguay (Chapter One) and thoroughly review Coxiella burnetii and Chlamydia abortus (Chapter Two). After this, two main sections will be presented. The first section including a systematic review and meta-analysis (Chapter Three), and the second section comprising the observational fieldwork studies conducted out on dairy farms in Uruguay, which includes a cross-sectional study of pooled milk (PM) samples from commercial herds (Chapter Four), a case-series sampling of placentas (Chapter Five), a case-control sampling of aborted and non-aborted dairy animals (Chapter Six), and finally a retrospective cohort evaluation of workers exposed to a local bovine Q fever outbreak (Chapter Seven). A final discussion (Chapter Eight) will consider the main findings' implications and integrate these results into the general body of knowledge. The systematic review and meta-analysis evidenced bulk tank milk (BTM) sampling as a broadly used epidemiological methodology for large-scale investigations of C. burnetii and provided a global framework of the prevalence of C. burnetii in collective milk samples from commercial farms. This study showed a widespread herd-level circulation of C. burnetii in bovine dairy farms by reporting a high overall global prevalence of 37.0% (CI95% 25.2-49.5%). A meta-regression showed the herd size as the most relevant moderator, with the odds of a BTM sample testing positive doubling with every unit increase. This C. burnetii meta-prevalence roles as a benchmark for comparison with the findings of the molecular investigation on PM samples obtained from local dairy farms. The mass-scale molecular evaluation on PM samples evidenced a low incidence (1.7%) of C. burnetii DNA. The findings showed that clinically healthy (asymptomatic) cows might shed the bacterium, raising awareness of Q fever as potential food safety and public health concern considering the C. burnetii survival as a milk-borne pathogen in unpasteurised milk and raw dairy products. Due to the exceptionally high infectivity, low infective doses, and aerosol transmission, the culture of C. burnetii and Chlamydiales should be done on BSL-3 laboratories not currently operating in Uruguay. Bacterial cultivation was not attempted in any of the studies conducted in this thesis. Hitherto the lack of diagnostic tools and the impossibility of doing culture have restricted local epidemiological investigation of these agents. Therefore, developing diagnostic tests to be used routinely in domestic laboratories is imperative to save costs and optimise currently available facilities and work with higher autonomy. For this purpose, a published protocol targeting well-evaluated genes was adapted to provide an available tool for local laboratories. Coxiella burnetii, C. abortus, and C. pecorum were investigated for the first time using an m-PCR in placentas from aborted dairy cows. Coxiella burnetii-DNA was detected and quantified in those samples, which supported this bacterium as an abortifacient agent in Uruguay. No co-infections of these pathogens were found. Evidence supporting Chlamydiales as a source of cattle abortion remain blurred. Coxiella burnetii was detected on the aborted placenta from a cow from an artisanal cheese-producing farm. Consumption of raw milk and dairy products represent a potential source for human infection. This finding underlined that the public health risk posed by C. burnetii should not be neglected and should be emphasised the need for on-farm milk pasteurisation by local artisanal cheesemakers. Molecular investigation of C. abortus in vulvo-vaginal swabs samples showed no evidence of this bacterium neither in aborted nor in control animals. Difficulties in identifying low-grade infection and evaluating a single sample per animal would have constrained the detection. The first attempted studies conducted so far support C. abortus as a no substantial abortifacient agent in cattle from Uruguay. Serological evidence confirmed the local bovine population as a potential reservoir for C. burnetii infection in humans. Anti-C. burnetii phase II IgM and IgG immunoglobulins were detected in a group of farmworkers and laboratory technicians exposed to aborted dairy cattle or aborted materials (fetuses and placenta) by indirect immunofluorescence. Molecular approaches were assessed, optimised and validated on veterinary clinical samples such as aborted placentas, vulvo-vaginal swabs or collective milk samples, providing valuable alternatives beyond the bacterial culture and isolation. The thesis presents original research studies that utilise different epidemiological strategies to search for evidence of an association between the infection by the pathogens and the occurrence of bovine abortion.Agencia Nacional de Investigación e InnovaciónInstituto Nacional de Investigación Agropecuari