Artículos Científicos

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A bvrR/bvrS Non-Polar Brucella abortus Mutant Confirms the Role of the Two-Component System BvrR/BvrS in Virulence and Membrane Integrity
(MDPI, 2023-08-05) Rivas-Solano, Olga; Núñez-Montero, Kattia; Altamirano-Silva, Pamela; Ruiz-Villalobos, Nazareth; BARQUERO-CALVO, ELIAS; Moreno, Edgardo; Chaves-Olarte, Esteban; Guzman-Verri, Caterina
Brucella abortus is a bacterial pathogen causing bovine brucellosis worldwide. This facultative extracellular–intracellular pathogen can be transmitted to humans, leading to a zoonotic disease. The disease remains a public health concern, particularly in regions where livestock farming is present. The two-component regulatory system BvrR/BvrS was described by isolating the attenuated transposition mutants bvrR::Tn5 and bvrS::Tn5, whose characterization led to the understanding of the role of the system in bacterial survival. However, a phenotypic comparison with deletion mutants has not been performed because their construction has been unsuccessful in brucellae and difficult in phylogenetically related Rhizobiales with BvrR/BvrS orthologs. Here, we used an unmarked gene excision strategy to generate a B. abortus mutant strain lacking both genes, called B. abortus ∆bvrRS. The deletion was verified through PCR, Southern blot, Western blot, Sanger sequencing, and whole-genome sequencing, confirming a clean mutation without further alterations at the genome level. B. abortus ∆bvrRS shared attenuated phenotypic traits with both transposition mutants, confirming the role of BvrR/BvrS in pathogenesis and membrane integrity. This B. abortus ∆bvrRS with a non-antimicrobial marker is an excellent tool for continuing studies on the role of BvrR/BvrS in the B. abortus lifestyle.
A sensor histidine kinase from a plant-endosymbiont bacterium restores the virulence of a mammalian intracellular pathogen
(Elsevier, 2023-11-08) Chaves-Olarte, Esteban; Meza-Torres, Jazmín; Herrera-Rodríguez, Fabiola; Lizano-González, Esteban; Suárez-Esquivel, Marcela; Baker, Kate S.; Rivas-Solano, Olga; Ruiz-Villalobos, Nazareth; Villalta-Romero, Fabián; Cheng, Hai-Ping; Walkerf, Graham C.; Cloeckaert, Axel; Thomson, Nicholas R.; Frisan, Teresa; Moreno, Edgardo; Guzman-Verri, Caterina
Alphaproteobacteria include organisms living in close association with plants or animals. This interaction relies partly on orthologous two-component regulatory systems (TCS), with sensor and regulator proteins modulating the expression of conserved genes related to symbiosis/virulence. We assessed the ability of the exoS+Sm gene, encoding a sensor protein from the plant endosymbiont Sinorhizobium meliloti to substitute its orthologous bvrS in the related animal/human pathogen Brucella abortus. ExoS phosphorylated the B. abortus regulator BvrR in vitro and in cultured bacteria, showing conserved biological function. Production of ExoS in a B. abortus bvrS mutant reestablished replication in host cells and the capacity to infect mice. Bacterial outer membrane properties, the production of the type IV secretion system VirB, and its transcriptional regulators VjbR and BvrR were restored as compared to parental B. abortus. These results indicate that conserved traits of orthologous TCS from bacteria living in and sensing different environments are sufficient to achieve phenotypic plasticity and support bacterial survival. The knowledge of bacterial genetic networks regulating host interactions allows for an understanding of the subtle differences between symbiosis and parasitism. Rewiring these networks could provide new alternatives to control and prevent bacterial infection.
A Sinorhizobium meliloti and Agrobacterium tumefaciens ExoR ortholog is not crucial for Brucella abortus virulence
(PLOS ONE, 2021-08-13) Castillo Zeledon, Amanda; Ruiz-Villalobos, Nazareth; Altamirano-Silva, Pamela; Chacón-Díaz, Carlos; BARQUERO-CALVO, ELIAS; Chaves-Olarte, Esteban; Guzman-Verri, Caterina
Brucella is a facultative extracellular-intracellular pathogen that belongs to the Alphaproteo- bacteria class. Precise sensing of environmental changes and a proper response mediated by a gene expression regulatory network are essential for this pathogen to survive. The plant-related Alphaproteobacteria Sinorhizobium meliloti and Agrobacterium tumefaciens also alternate from a free to a host-associated life, where a regulatory invasion switch is needed for this transition. This switch is composed of a two-component regulatory system (TCS) and a global inhibitor, ExoR. In B. abortus, the BvrR/BvrS TCS is essential for intra- cellular survival. However, the presence of a TCS inhibitor, such as ExoR, in Brucella is still unknown. In this work, we identified a genomic sequence similar to S. meliloti exoR in the B. abortus 2308W genome, constructed an exoR mutant strain, and performed its characteri- zation through ex vivo and in vivo assays. Our findings indicate that ExoR is related to the BvrR phosphorylation state, and is related to the expression of known BvrR/BrvS gene tar- gets, such as virB8, vjbR, and omp25 when grown in rich medium or starving conditions. Despite this, the exoR mutant strain showed no significant differences as compared to the wild-type strain, related to resistance to polymyxin B or human non-immune serum, intracel- lular replication, or infectivity in a mice model. ExoR in B. abortus is related to BvrR/BvrS as observed in other Rhizobiales; however, its function seems different from that observed for its orthologs described in A. tumefaciens and S. meliloti.
An Anatomical and Radiographic Study on the Vertebral Column of the Two-Toed Sloth (Choloepus hoffmanni)
(Universidad Nacional, Costa Rica, 2021-04-23) Chinchilla-Barboza, Maripaz; Chiquillo-Vergara, Siam; Delgado-Álvarez, Valeria; Gutiérrez- Gutiérrez, Susan; Mora-Aleman, Steven; Páez-Padilla, Jonathan Gerardo; Sanchez-Bermudez, Jorge; Pequeno, Andréia Passos
El Choloepus hoffmanni es un mamífero del superorden Xenarthra que se distribuye desde América Central hasta América del Sur. Estos animales comúnmente llegan a los centros de atención y valoración de fauna silvestre víctimas de atropellamientos o agresiones por parte del humano y animales domésticos, por lo que las bases anatómicas son fundamentales para la práctica clinico-quirúrgica en esta especie. El objetivo del presente trabajo fue describir las características anatómicas y radiográficas de la columna vertebral del Choloepus hoffmanni. En este estudio se utilizaron cuatro especímenes de C. hoffmanni, los huesos de la columna vertebral se prepararon mediante hervido y macerado. Como resultados fue posible observar que el esqueleto axial del perezoso está compuesto por cinco tipos de vértebras notablemente distintas. Entre ellas fueron encontradas seis vértebras cervicales, un número variable de vértebras torácicas, vértebras lumbares xenartéricas y la fusión entre el sacro y los coxales. Finalmente, fueron identificadas cuatro vértebras caudales subdesarrolladas formando un pequeño muñón de cola. Radiográficamente, no se observaron desvíos anormales en ninguno de los segmentos de la columna ni tampoco alteraciones óseas o de estructuras adyacentes. En conclusión, el presente estudio describió tanto la osteología como la anatomía radiológica de la columna vertebral del C. hoffmanni detallando las similitudes y particularidades de esta especie en relación con mamíferos domésticos, así como otras especies del superorden Xenartra. Tal información es importante para el análisis forense de la vida silvestre, así como colaborar con el abordaje clínico-quirúrgico de lesiones en la columna vertebral en esta especie.
Análisis de las causas más frecuentes de decomisos de vísceras en cerdos, en un matadero de Costa Rica y su implicación económica
(Revista Porcicultura Iberoamericana, 2011) Pequeno, Andréia Passos; Mateus Vargas, Rafael Hernan; Alfaro Zúñiga, Carlos Eduardo; Jimenez Loaiza, Emily María
Antimicrobial resistance and genetic diversity of Campylobacter spp. isolated from broiler chicken at three levels of the poultry production chain in Costa Rica
(International Association for Food Protection, 2021-07-29) Lazo Láscarez, Sabrina; Zumbado Gutiérrez, Leana; Duarte-Martínez , Francisco; ROMERO-ZUÑIGA, JUAN JOSE; Arias Echandi, María Laura; MUNOZ VARGAS, LOHENDY
Campylobacter spp. are considered the most common bacterial cause of human gastroenteritis, one of the four main causes of diarrheal disease worldwide, and they are one of the main foodborne pathogens causing hospitalizations and deaths. Here, 148 strains of Campylobacter spp. isolated from poultry at farms, processing plants, and retail stores in Costa Rica were examined for resistance to six antibiotics. An agar dilution test was used to determine the MIC and susceptibility profiles against doxycycline, ciprofloxacin, nalidixic acid, enrofloxacin, chloramphenicol, and erythromycin. In addition, a pulsed-field gel electrophoresis analysis was carried out to determine the genotype relatedness of a representative subset of the isolates. Approximately 136 (92%) of the 148 analyzed isolates showed resistance to the tested drugs. Nalidixic acid, ciprofloxacin, and enrofloxacin were the antibiotics for which resistance occurred most frequently (91.2, 85.8, and 85.8%, respectively); followed by doxycycline (25.0%), chloramphenicol (5.4%), and erythromycin (2.7%). The profile conferring only resistance to quinolones was the most frequently found, and only 2.0% of the isolates showed resistance to quinolones and macrolides simultaneously. Results showed a high frequency of resistant Campylobacter spp. strains and evidenced the distribution, selection, and circulation of resistant strains along the poultry chain from farms to consumers. Cross-contamination and resistance seem to play important roles in the dissemination of these strains at specific points of the poultry chain, even when control measures are being taken. The establishment of effective surveillance and control strategies represents an essential tool for foodborne diseases mitigation. The rational use of antibiotics, especially those still showing efficacy, should be a priority in both human and veterinary medicine to contain the progress of this phenomenon and its consequences.
Aspergillus spp. Isolated from Lungs of Poultry (Gallus gallus) at the Mycology Laboratory, School of Veterinary Medicine, Universidad Nacional, Heredia, Costa Rica between 2008 and 2021 and Associated Factors
(MDPI, 2022-11-30) Ulloa-Avellán, Óscar; Calderón Hernández, Alejandra; Rubí Chacón, Randall; Vargas Leitón, Bernardo
Aspergillosis is a disease caused by some species of the fungus Aspergillus, occurring in both mammals (including humans) and birds, the latter being the most susceptible group. Aspergillus must be considered a public health concern as it affects the poultry industry economically and is an occupational risk to its workers. A retrospective study of fungal isolates from the lungs of chickens (Gallus gallus), analyzed between 2008 and 2021 at the Mycology Laboratory, School of Veterinary Medicine, Universidad Nacional, Heredia, Costa Rica was performed to report the prevalence of Aspergillus spp. in poultry farms in Costa Rica and their associated factors. A total of 1113 cases were received, of which 31% (n = 392; 95% CI: 28.3–33.7) were positive for fungal isolation. Aspergillus was the most frequently detected genus, and the most frequent sections were Fumigati (n = 197/392, 50.3%), Flavi (n = 90/392, 22.9%), and Nigri (n = 50/392, 12.7%). Significant effects (p < 0.05) related to the year, geographical origin, purpose, and age were identified in relation to the Aspergillus infection. The identified factors are explained by climatic variations in the tropics and the particularities of the birds. Future research including molecular characterization and antifungal susceptibility tests in animals, humans, and the environment, are needed to better understand the risks of the diseases caused by those fungi in this country.
Brucella sp. sequence‑type 27 associated with abortion in dwarf sperm whale Kogia sima
(Springer Link, 2021-05-18) Hernández-Mora, Gabriela; González-Barrientos, Rocío; Víquez‑Ruíz, Eunice; Palacios Alfaro, Jose David; Bettoni‑Rodríguez, Gianmarco; Gendre, Marlène; Vincent, Charline; Roca‑Monge, Karol; Ruiz-Villalobos, Nazareth; Suárez-Esquivel, Marcela; Cordero‑Chavarría, Minor; Chaves-Olarte, Esteban; Thomson, Nicholas R.; BARQUERO-CALVO, ELIAS; Moreno, Edgardo; Guzman-Verri, Caterina
A dwarf sperm whale Kogia sima stranded alive along the Central Pacifc Coast of Costa Rica. The whale, handled by tourists and local inhabitants, was weak, had buoyancy difculties, and eventually aborted and died, showing severe necrotizing placentitis and other pathological signs. Both the mother and the fetus had antibodies against Brucella lipopolysaccharide. Brucella organisms were isolated from various tissues of both animals and were characterized. The bacterium genome corresponded to sequence-type 27 (ST27) and clustered together with other Brucella ST27 isolated in humans and cetaceans.
Carcinogenicidad del Pteridium Aquilinum y alta incidencia del Cancer Gástrico en Costa Rica
(Caja Costarricense de Seguro Social, 1985-08) Salazar Villalobos, Jorge
Se estudió la correlación entre consumo de leche potencialmente contaminada con factores caracinogénicos del Pteridium aquilinum y la alta incidencia del cáncer gástrico en Costa Rica. La contaminación de la leche se determinó por la presencia de Pteridium aquilinum en los potreros y la incidencia de hematuria enzoótica en el ganado que pasta en ellos, en diferentes regiones del país. Se encontró una correlación positiva entre consumo de leche contaminada e incidencia de cáncer gástrico. Los potreros de zonas con alta o muy alta incidencia de cáncer gástrico están invadidos por Pteridium aquilinum y presentan alta incidencia de hematuria enzoótica. Los potreros de zonas con baja prevalencia de cáncer gástrico están libres de Pteridium aquilinum y de hematuria enzoótica bovina. Se concluye que la leche de bovinos que pastan en potreros invadidos por Pteridium aquilinum debe ser considerada como un posible factor etiológico del cáncer gástrico.
Case report: First documented case of cerebral angiostrongyliasis caused by Angiostrongylus costaricensis in a free-ranging opossum
(Frontiers, 2024-02-01) Solorzano-Scott, Tamara; Aguilar-Vargas, Fernando; Cordero-Salas, Martha; Conejo, Amanda; Rojas, Alicia; Baldi, Mario
Angiostrongylus costaricensis is a metastrongyloid nematode that primarily infects the mesenteric arteries of wild rodents. This parasite is endemic in several regions of the American continent, and in humans, causes a disease known as abdominal angiostrongyliasis. Despite the important health implications of this nematode, there are limited studies investigating the involvement of wild animals in its life cycle. In this study, we present the clinical manifestations, pathologic findings, and molecular diagnosis, to the best of our current knowledge, of the first documented onset of cerebral angiostrongyliasis because of A. costaricensis infection in a juvenile free-ranging opossum (Didelphis marsupialis). Histopathological findings stress the presence of eosinophilic meningoencephalitis with nematodes present within the lesions, and PCR was positive for cox1 and ITS1 reactions. The obtained sequences for a 279 bp fragment of ITS1 were 100% identical to A. costaricensis from Costa Rica. This case highlights the substantial difficulties in diagnosing neuroangiostrongyliasis, yet underscores the importance of considering A. costaricensis as a potential culprit behind neurological conditions in wild marsupials. It acts as an urgent call to action to improve surveillance programs tracking infectious and parasitic diseases causing mortality in wildlife populations.
Comamonas testosteroni as the cause of mortality in embryonated chicken eggs of breeding broiler hens in Costa Rica
(Taylor and Francis Group, 2023-12) Chaves-Hernandez, Aida Jeannette; BARQUERO-CALVO, ELIAS; Quesada-Vasquez, Dioney; Chacón-Díaz, Carlos
Mortality of chicken embryos andfirst-week chickens was reported in a commercial incubatorcompany in Costa Rica. Six 1-day-old Cobb chickens and twenty-four embryonated chickeneggs were examined in the Laboratory of Avian Pathology and the Laboratory ofBacteriology of the National University of Costa Rica. Twelve dead-in-shell embryos showedmaceration and were immersed in a putrid, turbid, slightly thick brown liquid. Additionally,the other 12 embryonated eggs had milky yellow-orange content. The livers of thoseembryos had congestion, haemorrhages and multifocal cream foci of necrosis. Granulocyticinfiltration was observed in the bursa of Fabricius, myocardium, liver, lung and kidney. Liversand egg yolks from six embryonated chickens and all 1-day-old chickens were asepticallycollected and cultured. In addition, tissues from six better conserved embryos and all 1-day-old chickens werefixed in buffered formalin and embedded in paraffin. Biochemical andmolecular tests identifiedComamonas testosteronias the cause of the early, middle and lateembryo mortality. As all the eggshells from the sampled embryonated eggs were dirty withsoiled a fecal matter, contamination after manipulating the eggs was considered the sourceof infection.C. testosteroniis an environmental microorganism that has rarely been reportedto cause human disease. To our knowledge, this is thefirst report ofC. testosteronicausingmortality in a hatchery. Cleaning and disinfection using ozone were implemented in thehatchery to eliminate the embryo mortality associated withC. testosteroni.
Comparison of Agar Gel Immunodiffusion Test, Enzyme-linked Immunosorbent Assay and Western Blotting for the Detection of BLV Antibodies
(Blackwell, 1999-10) Dolz, Gaby; Moreno, Edgardo
An indirect enzyme-linked immunosorbent assay (ELISA) for the diagnosis of bovine leukaemia virus (BLV) infection was developed and compared with the agar gel immunodiffusion test (AGIDT). Western blotting (WB) was used as confirmatory test. ELISA and AGIDT had specificities that were comparable with that of WB, however, ELISA showed a higher sensitivity than AGIDT. The ELISA was useful for screening a large number of samples, whereas WB was important for detecting the antibody response against the individual BLV-proteins. Different types of positive serological reactions were discerned in WB, that correlated with reactions of sera in AGIDT and ELISA. The most important antigen in WB and ELISA was the BLV protein p24, whereas the BLV glycoproteins gp51 and gp30 were of special importance in AGIDT. The relevance of repeatedly testing the antibody response in BLV-infected herds for control and eradication programmes using assays with higher sensitivity than AGIDT was demonstrated.
Cryptic diversity in a gastrointestinal acanthocephalan of New World primates from Costa Rica
(Springer Nature, 2023-02-10) Rojas Sánchez, Ernesto; Umaña‑Blanco, Fabián; Jiménez Rocha, Ana Eugenia; Vega-Benavides, Karen ; Medaglia, Alejandro; Solano‑Barquero, Alberto; Rojas, Alicia; Jiménez Soto, Mauricio
Prosthenorchis elegans is a worm of the family Archiacanthocephala that infects non-human primates in the Americas, producing an intestinal pathology that may compromise the life of its hosts. Squirrel monkeys, Saimiri oerstedii citrinellus, were found with P. elegans in Costa Rica. Histopathological analysis revealed a severe pyogranulomatous response composed by macrophages, neutrophils, eosinophils, fibroblasts and lymphocytes. Morphological worm analyses revealed 36 hooks in the proboscis distributed in six rows; and total body, hook and lemnisci length were compatible to the original descriptions of P. elegans. In addition, phylogenetic, haplotype network and genetic distance analyses were done on cytochrome oxidase subunit 1, cox1, sequences obtained from the collected specimens. Sequences obtained herein clustered separately with high posterior probabilities in a Bayesian Inference tree and showed 8.12% nucleotide differences when compared to P. elegans from Colombia. This high divergence was confirmed in the TCS network that separated Colombian and Costa Rican sequences by 32 mutational steps, a genetic distance PCA which separated sequences from both geographical locations by 89.5% and an FST value of 0.655, indicating the presence of cryptic diversity in P. elegans. Additional studies from specimens collected from other definitive hosts and geographical locations are required to better understand the biodiversity of this species.
Detection of Human Paragonimiasis by ELISA Using Recombinant Paragonimus westermani Cysteine Protease 7
(The American Society of Tropical Medicine and Hygiene, 2023-05) Andrade-Gomes, Luana Gabriele; Zuniga, MarÍa J.; Dolz, Gaby; Solano-Campos, Frank
Paragonimiasis is an important but neglected foodborne trematodiasis caused by Paragonimus mexicanus in Costa Rica. Immunological techniques for diagnosing this parasitosis in humans do not exist in Central America. The objective of the present study was to use recombinant Paragonimus westermani cysteine protease 7 to standardize an ELISA for the detection of antibodies against Paragonimus spp. Human sera positive for P. westermani, P. mexicanus, or Paragonimus spp., human sera infected with other helminths, as well as sera of healthy humans without parasitic infections, were analyzed. The sensitivity of the ELISA was 92.9%, and the specificity was 91.9%. This report is the first to describe the development of an ELISA for the diagnosis of Paragonimus spp. in Costa Rica and Central America. Using this ELISA in the health system of Costa Rica is recommended to detect infections.
Detection of Venezuelan Equine Encephalitis Virus from Brain Samples of Equines with Encephalitis
(MDPI, 2023) León, Bernal; Estrella-Morales, Josimar; Jiménez Sánchez, Carlos
Alphavirus species are globally distributed zoonoses primarily transmitted by arthropods. The Venezuelan equine encephalitis virus (VEEV) and Eastern equine encephalitis virus (EEEV) are endemic in Costa Rica. This study aims to detect these viruses in brain samples from equines displaying nervous signs. For this purpose, four published Universal RT-PCR methods were compared. The most sensitive and specific RT-PCR method was used to test a total of 70 brain samples, including 40 from bovines and 30 from equines, all exhibiting nervous signs. In the positive cases, eight different brain regions were extracted and tested using this RT-PCR. Positive cases were confirmed through sequencing. Torii RT-PCR demonstrated the highest sensitivity and specificity for diagnosing VEEV and EEEV/Sind among the four Universal RT-PCR assays. Not all assessed brain regions showed DNA amplification. None of the bovine brains was positive, and out of the 30 equine brain samples, only four tested positive, and sequencing confirmed two of these samples as VEEV subtype IE. Torii RT-PCR successfully detected VEEV in pools of the hippocampus, spinal cord, and basal nuclei, making these brain regions suitable for diagnosing this virus. None of the samples were positive for EEEV or WEEV.
Determination of streptomycin and doxycycline using LC/MS towards an effective treatment against an experimental Brucella abortus infection in mice
(Elsevier B.V, 2022-02-25) Sancho, Eugenia; Granados, Fabio; BARQUERO-CALVO, ELIAS
Herein we described a versatile liquid chromatographic method for detection and quantification of the total levels of two antimicrobials [i.e., streptomycin (STM) and doxycycline (DOX)], in mice plasma and selected tissues, with the aid of a single quadrupole as a detection method. The method included a few sample preparation steps, including freeze-drying and in situ triphasic solvent-assisted defatting, precipitation, and extraction, allowing easy and fast tissue sample processing and avoiding analyte loss. Using a murine model, we demonstrated that mass spectrometry detects simultaneously and with high specificity two of the most widespread antimicrobials used against Brucellosis. An accurate [recoveries varied from 75.23 (bone marrow) to 101.33% (liver)] and sensitive (LoD in the ng g− 1 range) method to assess STM and DOX in murine tissue, including subtherapeutic and therapeutic doses of the antimicrobials, was achieved. This validated method can be successfully used to monitor the depletion of STM and DOX in several mice tissues and plasma during metabolism after administration.
Editorial: Insights in infectious agents and disease: 2021
(Frontiers Media S.A, 2023-07-10) Cloeckaert, Axel; Guzman-Verri, Caterina
The emergence and spread of infectious diseases with pandemic potential occurred trough human history, and were recently reviewed in the section Infectious Agents and Disease by Piret and Boivin (2021). Major pandemics and epidemics involved bacterial infectious diseases such as plague, cholera, or tuberculosis since past centuries, and viral infectious diseases such as flu and the most recently COVID-19 which emerged at the end of 2019, spread globally, and caused millions of deaths. Many infectious diseases leading to pandemics are caused by zoonotic pathogens, originating from an animal source (livestock, wildlife, or companion animals). In addition, some of them may be transmitted to humans through intermediate hosts such as arthropods, which allow them to be grouped as vector-borne and zoonotic infectious diseases. The present Research Topic, consisting of 36 published articles, provides an overview of recent developments in the field of bacterial, viral, parasitic, and fungal infectious diseases. This overview can be structured according to the type of infectious agent concerned, i.e., mainly bacterial, viral, or fungal, and in the order of importance according to the number of articles published for each infectious agent type. It also reflects the current content of the section Infectious Agents and Disease of Frontiers in Microbiology.
Effect of age at first calving on first lactation milk yield in Holstein cows from Costa Rican specialized dairy herds
(Scientific Research Publishing, 2014-09) Salazar Carranza, Mauren; Castillo Badilla, Gloriana; Murillo Herrera, Jaime; Hueckmann Voss, Frank; ROMERO-ZUÑIGA, JUAN JOSÉ
In order to determine the effect of age at first calving (AFC) at 305-d milk yield, a historical prospective longitudinal study of 46,029 pure specialized dairy Costa Rican Holstein animals was carried out between 2000 and 2010. Data on purebred specialized dairy Holstein cows enrolled in the program VAMPP Bovino 3.0 were included. Information was analyzed by using descriptive statistics and mixed linear models. The effect of the AFC was adjusted to the ecological zone, season of birth, year of birth, inbreeding index, and type of parturition and parity number of the dam at birth. The average AFC for the animals that were part of the study was 30.7 mo (SD: 6.8, 95% CI: 30.6 - 30.7). The average total milk production in the first lactation was 5188.0 kg (95% CI: 5153.4 - 5223.2), whereas the 305-d corrected milk yield resulted in 5288 kg (95% CI: 5253.7 - 5323.2). Cows with AFC less than 26 mo and between 26.0 and 33.6 mo, produced −354.8 kg/305-d (P <0.0001) and −105.6 kg/305-d (P = 0.0117) respectively, compared with cows calving over 33.6 mo. It is likely that the observed effect of the AFC on the topmost dairy lactation affects the productive life of the cow within the herd. Further studies are required to prove this hypothesis.
Effect of neosporosis on productive and reproductive performance of dairy cattle in Costa Rica
(Elsevier B.V, 2005-12) ROMERO-ZUÑIGA, JUAN JOSÉ; Van Breda, S.; Vargas, Bernardo; Dolz, Gaby; Frankena, K.
A cross-sectional study was conducted to assess the effect of neosporosis on productive and reproductive parameters in dairy cows. Cows (n = 2743) from 94 farms located in the most important dairy areas in Costa Rica were used in the study. The size of the herds ranged from 32 to 379 females (mean = 110, median = 125). An indirect ELISA was used to determine the serostatus of the cows towards Neospora caninum. The effect of neosporosis on milk production was analysed by a mixed linear model. In addition, the effects on calving interval (days) and calving to conception interval (days) were analysed by survival analysis. The risk of abortion in relation to N. caninum serostatus was assessed by logistic regression, with herd as a random effect. Overall, 1185 of 2743 cows (43.3%) were seropositive for Neospora. Eighty-nine of 94 (94.7%) farms were classified as Neospora-seropositive. It was estimated that cows seronegative to Neospora produced an additional 84.7 L of milk (P = 0.6). Serostatus did not have a significant effect on the length of the calving interval in the Cox proportional hazard survival analysis (Hazard ratio = 1.2, 95% CI: 0.9, 1.4). The logistic regression model had a weak positive association between serostatus and abortion (OR 1.7, 95% CI: 0.8, 3.9), but did not show a strong association between serostatus and the number of services per conception (OR = 0.95, 95% CI: 0.7, 1.3). In conclusion, there were no significant effects of Neospora serostatus on production and reproductive performance in this study.
Effect of the use of probiotic Bacillus subtilis (QST 713) as a growth promoter in broilers: an alternative to bacitracin methylene disalicylate
(Elsevier Inc. on behalf of Poultry Science Association Inc, 2021-06-29) Rivera-Perez, Walter; BARQUERO-CALVO, ELIAS; Chaves Hernández, Aida J.
The global poultry trend toward the more responsible use of antibiotics is becoming recurrent and has demanded the need to generate new natural alternatives. Probiotics have gained importance as an option to use as growth promoters. This study aimed to evaluate Bacillus subtillis QST713 as a substitute for an antibiotic growth promoter (BMD). A total of 150 male broilers were assigned to three dietary treatments: 1) control diet (CO), 2) control diet + 500 g/t of BMD (AGP), and 3) control diet + 100 g/t of B. subtilis QST713 (PB), respectively. Each treatment was monitored for 5 wk for the productive variables: body weight, accumulated feed consumption, food conversion, and European efficiency factor. At the end of each week, fresh fecal samples were cultured and quantified for E. coli, Enterococcus spp., and Lactobacillus spp. At the end of the trial, blood samples were analyzed for hemogram and intestinal samples (anterior portion) for histomorphometry. The data were statistically analyzed with an analysis of variance and subjected to a least significant difference test (Tukey). The zootechnical yields were similar in the AGP and PB groups (P ˃ 0.05); both superior to the control group. In the hematological profiles, no difference was observed between the experimental groups. E. coli and Enterococcus counts were significantly lower (P ˂ 0.05), and Lactobacillus counts were significantly (P ˂ 0.05) higher in the PB group, relative to CO and AGP groups. No differences (P ˃ 0.05) were found in bacterial counts between the CO and AGP groups. The intestinal mucosa and villi in the PB group were significantly (P ˂ 0.05) longer and with less deeper crypts than CO and AGP groups. We conclude that B. subtillis QST713, used at the suggested commercial dose (100 g/ton), is an effective growth-promoting alternative to BMD that modulates the microbiota and intestinal architecture, thus producing zootechnical yields consistent with BMD.

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