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Benefits and costs of immune memory in Rhodnius prolixus against Trypanosoma cruzi. Microb Pathog 2022; 165:105505. [PMID: 35341956 DOI: 10.1016/j.micpath.2022.105505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 03/23/2022] [Accepted: 03/23/2022] [Indexed: 10/18/2022]
Abstract
There is increasing evidence supporting the immune memory in invertebrates, but the studies are relatively neglected in insect vectors other than mosquitoes. Therefore, we tested two hypotheses: 1) Rhodnius prolixus insects possess immune memory against Trypanosoma cruzi, and 2) their immune memory is costly. The Dm28c and Y strains of T. cruzi were used, the former being more infective than the latter. On the one hand, the triatomines subjected to dual challenges with the Dm28c strain did not show significant differences in survival than those of the heterologous challenge groups control-Dm28c and Y-Dm28c. On the other hand, the insects survived longer after a dual Y-Y challenge than after the corresponding heterologous challenge (control-Y). The Y-Y, Dm28c-Y, and naïve groups showed similar survival. There was more prolonged survival following the Y-Y versus Dm28c-Dm28c dual challenge. The Dm28c-Dm28c group exhibited moulting sooner than the control-Dm28c or naïve group. In contrast, there were no differences in the probability of moulting between the Y-Y and naïve groups. The results suggest that triatomines have immune memory against the Y but not the Dm28c strain. Further investigation on triatomine and T. cruzi interaction is needed to determine if infectivity accelerates or delay growth due to innate immune memory.
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Genetic diversity of Bm86 sequences in Rhipicephalus (Boophilus) microplus ticks from Mexico: analysis of haplotype distribution patterns. BMC Genet 2019; 20:56. [PMID: 31299900 PMCID: PMC6626424 DOI: 10.1186/s12863-019-0754-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 06/20/2019] [Indexed: 11/25/2022] Open
Abstract
Background Ticks are a problem for cattle production mainly in tropical and subtropical regions, because they generate great economic losses. Acaricides and vaccines have been used to try to keep tick populations under control. This has been proven difficult given the resistance to acaricides and vaccines observed in ticks. Resistance to protein rBm86-based vaccines has been associated with the genetic diversity of Bm86 among the ectoparasite’s populations. So far, neither genetic diversity, nor spatial distribution of circulating Bm86 haplotypes, have been studied within the Mexican territory. Here, we explored the genetic diversity of 125 Bm86 cDNA gene sequences from R. microplus from 10 endemic areas of Mexico by analyzing haplotype distribution patterns to help in understanding the population genetic structure of Mexican ticks. Results Our results showed an average nucleotide identity among the Mexican isolates of 98.3%, ranging from 91.1 to 100%. Divergence between the Mexican and Yeerongpilly (the Bm86 reference vaccine antigen) sequences ranged from 3.1 to 7.4%. Based on the geographic distribution of Bm86 haplotypes in Mexico, our results suggest gene flow occurrence within different regions of the Mexican territory, and even the USA. Conclusions The polymorphism of Bm86 found in the populations included in this study, could account for the poor efficacy of the current Bm86 antigen based commercial vaccine in many regions of Mexico. Our data may contribute towards designing new, highly-specific, Bm86 antigen vaccine candidates against R. microplus circulating in Mexico.
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PTML Model for Proteome Mining of B-Cell Epitopes and Theoretical–Experimental Study of Bm86 Protein Sequences from Colima, Mexico. J Proteome Res 2017; 16:4093-4103. [DOI: 10.1021/acs.jproteome.7b00477] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Immune protection against Trypanosoma cruzi induced by TcVac4 in a canine model. PLoS Negl Trop Dis 2015; 9:e0003625. [PMID: 25853654 PMCID: PMC4390229 DOI: 10.1371/journal.pntd.0003625] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 02/16/2015] [Indexed: 12/02/2022] Open
Abstract
Chagas disease, caused by Trypanosoma cruzi, is endemic in southern parts of the American continent. Herein, we have tested the protective efficacy of a DNA-prime/T. rangeli-boost (TcVac4) vaccine in a dog (Canis familiaris) model. Dogs were immunized with two-doses of DNA vaccine (pcDNA3.1 encoding TcG1, TcG2, and TcG4 antigens plus IL-12- and GM-CSF-encoding plasmids) followed by two doses of glutaraldehyde-inactivated T. rangeli epimastigotes (TrIE); and challenged with highly pathogenic T. cruzi (SylvioX10/4) isolate. Dogs given TrIE or empty pcDNA3.1 were used as controls. We monitored post-vaccination and post-challenge infection antibody response by an ELISA, parasitemia by blood analysis and xenodiagnosis, and heart function by electrocardiography. Post-mortem anatomic and pathologic evaluation of the heart was conducted. TcVac4 induced a strong IgG response (IgG2>IgG1) that was significantly expanded post-infection, and moved to a nearly balanced IgG2/IgG1 response in chronic phase. In comparison, dogs given TrIE or empty plasmid DNA only developed high IgG titers with IgG2 predominance in response to T. cruzi infection. Blood parasitemia, tissue parasite foci, parasite transmission to triatomines, electrocardiographic abnormalities were significantly lower in TcVac4-vaccinated dogs than was observed in dogs given TrIE or empty plasmid DNA only. Macroscopic and microscopic alterations, the hallmarks of chronic Chagas disease, were significantly decreased in the myocardium of TcVac4-vaccinated dogs. We conclude that TcVac4 induced immunity was beneficial in providing resistance to T. cruzi infection, evidenced by control of chronic pathology of the heart and preservation of cardiac function in dogs. Additionally, TcVac4 vaccination decreased the transmission of parasites from vaccinated/infected animals to triatomines.
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Preventive and therapeutic DNA vaccination partially protect dogs against an infectious challenge with Trypanosoma cruzi. Vaccine 2013; 31:2246-52. [DOI: 10.1016/j.vaccine.2013.03.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 02/06/2013] [Accepted: 03/04/2013] [Indexed: 10/27/2022]
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Antigenicity and diagnostic potential of vaccine candidates in human Chagas disease. PLoS Negl Trop Dis 2013; 7:e2018. [PMID: 23350012 PMCID: PMC3547861 DOI: 10.1371/journal.pntd.0002018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 12/04/2012] [Indexed: 12/15/2022] Open
Abstract
Background Chagas disease, caused by Trypanosoma cruzi, is endemic in Latin America and an emerging infectious disease in the US and Europe. We have shown TcG1, TcG2, and TcG4 antigens elicit protective immunity to T. cruzi in mice and dogs. Herein, we investigated antigenicity of the recombinant proteins in humans to determine their potential utility for the development of next generation diagnostics for screening of T. cruzi infection and Chagas disease. Methods and Results Sera samples from inhabitants of the endemic areas of Argentina-Bolivia and Mexico-Guatemala were analyzed in 1st-phase for anti-T. cruzi antibody response by traditional serology tests; and in 2nd-phase for antibody response to the recombinant antigens (individually or mixed) by an ELISA. We noted similar antibody response to candidate antigens in sera samples from inhabitants of Argentina and Mexico (n = 175). The IgG antibodies to TcG1, TcG2, and TcG4 (individually) and TcGmix were present in 62–71%, 65–78% and 72–82%, and 89–93% of the subjects, respectively, identified to be seropositive by traditional serology. Recombinant TcG1- (93.6%), TcG2- (96%), TcG4- (94.6%) and TcGmix- (98%) based ELISA exhibited significantly higher specificity compared to that noted for T. cruzi trypomastigote-based ELISA (77.8%) in diagnosing T. cruzi-infection and avoiding cross-reactivity to Leishmania spp. No significant correlation was noted in the sera levels of antibody response and clinical severity of Chagas disease in seropositive subjects. Conclusions Three candidate antigens were recognized by antibody response in chagasic patients from two distinct study sites and expressed in diverse strains of the circulating parasites. A multiplex ELISA detecting antibody response to three antigens was highly sensitive and specific in diagnosing T. cruzi infection in humans, suggesting that a diagnostic kit based on TcG1, TcG2 and TcG4 recombinant proteins will be useful in diverse situations. Chagas disease is the most common cause of congestive heart failure related deaths among young adults in the endemic areas of South and Central America and Mexico. Diagnosis and treatment of T. cruzi infection has remained difficult and challenging after 100 years of its identification. In >95% of human cases, T. cruzi infection remains undiagnosed until several years later when chronic evolution of progressive disease results in clinical symptoms associated with cardiac damage. Diagnosis generally depends on the measurement of T. cruzi–specific antibodies that can result in false positives. A conclusive diagnosis of T. cruzi infection thus often requires multiple serological tests, in combination with epidemiological data and clinical symptoms. In this study, we investigated the antibody response to TcG1, TcG2, and TcG4 in clinically characterized chagasic patients. These antigens were identified as vaccine candidates and shown to elicit protective immunity to T. cruzi and Chagas disease in experimental animals. Our data show the serology test developed using the TcGmix (multiplex ELISA) is a significantly better alternative to epimastigote extracts currently used in T. cruzi serodiagnosis or the trypomastigote lysate used in this study for comparison purposes.
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Seroprevalence survey of American trypanosomiasis in Central Valley of Toluca. ScientificWorldJournal 2012; 2012:450619. [PMID: 22649293 PMCID: PMC3353279 DOI: 10.1100/2012/450619] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 11/30/2011] [Indexed: 11/18/2022] Open
Abstract
American trypanosomiasis is a growing health issue in the Americas. México is an endemic country, where some locations such as in the State of México are considered highly prevalent. In the valley of Toluca city, the capital of the State of Mexico, there exists an apparent high prevalence in dogs. The absence of triatomine vectors suggests that dogs may not be infected. Therefore, we conducted a directed survey to domiciliated and nondomiciliated dogs to reassess dogs' T. cruzi seroprevalence status. HAI and ELISA serologic tests were applied to 124 and 167 serums of domiciliated and nondomiciliated dogs in the target city. Risk factors were estimated, but the results did not show any evidence to assess them. No domiciliated dogs tested positive to both tests, whereas only one non-domiciliated dog resulted positive. This animal may have acquired the infection in an endemic area and then migrated to Toluca. Research results indicate that T. cruzi infection is not actively transmitted among dogs, and it is pointed out that dogs are the main sentinel animal population to evaluate a possible expansion of the territory affected by Chagas' disease.
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Evaluation of clinical and immunopathological features of different infective doses of Trypanosoma cruzi in dogs during the acute phase. ScientificWorldJournal 2012; 2012:635169. [PMID: 22547991 PMCID: PMC3323355 DOI: 10.1100/2012/635169] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2011] [Accepted: 11/28/2011] [Indexed: 11/17/2022] Open
Abstract
Infection with Trypanosoma cruzi is a major risk in Latin America, and dogs are believed to be good models for evaluating Chagas disease. Here, we evaluated the clinical and immunopathological alterations developed by mongrel dogs experimentally infected with different infective doses (2,000, 20,000, and 200,000 metacyclic trypomastigotes of Sylvio X10/4 strain kg−1 via intraperitoneal). Clinical and electrocardiographic parameters, as well as antibody production and pathologic lesions were evaluated. All three doses of this strain of T. cruzi induced a similar pattern of infection characterized by cardiac arrhythmias and severe and diffuse myocarditis. Specific anti-T. cruzi IgG indicated seroconversion by day 14 after infection, and IgG levels increased during the period of evaluation. Mortality was observed only in dogs infected with the medium or high parasite doses, but not in the group infected with a low dose of 2,000 parasites kg−1. Infection with a low dose of parasites provides an excellent nonlethal model to evaluate the immunopathology of the acute disease in dogs infected with the Sylvio X10/4 strain of T. cruzi.
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Trypanosoma cruzi in dogs: electrocardiographic and echocardiographic evaluation, in Malinalco, State of Mexico. Res Rep Trop Med 2011; 2:155-161. [PMID: 30881190 PMCID: PMC6415576 DOI: 10.2147/rrtm.s21683] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Chagas disease caused by Trypanosoma cruzi is an important public health problem in Latin America. Dogs are considered a risk factor for human Chagas disease, a sentinel for T. cruzi infection in endemic regions and an animal model to study pathological aspects of the disease. The potential use of dogs as indicators of human cardiac pathogenicity of local T. cruzi strains has been studied insufficiently. We studied electrocardiographic (EKG) and echocardiographic (ECG) alteration frequencies observed in an open population of dogs in Malinalco, Mexico, and determined if such frequencies were statistically associated with T. cruzi infection in dogs. Animals (n = 139) were clinically examined and owners were asked to answer a questionnaire about dogs' living conditions. Two commercial serological tests (IHA, ELISA) were conducted to detect anti-T. cruzi serum antibodies. Significant differences between seropositive and seronegative animals in cardiomyopathic frequencies were detected through EKG and ECG (P < 0.05). Thirty dogs (21.58%) were serologically positive to anti-T. cruzi antibodies (to ELISA and IHA assays), of which nine (30%) had EKG and/or ECG alterations. From the remaining 104 (78.42%) seronegative animals, five (4.5%) had EKG and/or ECG abnormalities. Our data support the hypothesis that most EKG and ECG alterations found in dogs from Malinalco could be associated with T. cruzi infection. Considering the dog as a sentinel and as an animal model for Chagas disease in humans, our findings suggest that the T. cruzi strains circulating in Malinalco have the potential to produce cardiomyopathies in infected humans.
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Abstract
The pathology of Chagas disease presents a complicated and diverse picture in humans. The major complications and destructive evolutionary outcomes of chronic infection by Trypanosoma cruzi in humans include ventricular fibrillation, thromboembolism and congestive heart failure. Studies in animal models and human patients have revealed the pathogenic mechanisms during disease progression, pathology of disease and features of protective immunity. Accordingly, several antigens, antigen-delivery vehicles and adjuvants have been tested to elicit immune protection to T. cruzi in experimental animals. This review summarizes the research efforts in vaccine development against Chagas disease during the past decade.
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Testing the efficacy of a multi-component DNA-prime/DNA-boost vaccine against Trypanosoma cruzi infection in dogs. PLoS Negl Trop Dis 2011; 5:e1050. [PMID: 21625470 PMCID: PMC3098890 DOI: 10.1371/journal.pntd.0001050] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 04/15/2011] [Indexed: 11/19/2022] Open
Abstract
Background Trypanosoma cruzi, the etiologic agent of Chagas Disease, is
a major vector borne health problem in Latin America and an emerging
infectious disease in the United States. Methods We tested the efficacy of a multi-component DNA-prime/DNA-boost vaccine
(TcVac1) against experimental T. cruzi infection in a
canine model. Dogs were immunized with antigen-encoding plasmids and
cytokine adjuvants, and two weeks after the last immunization, challenged
with T. cruzi trypomastigotes. We measured antibody
responses by ELISA and haemagglutination assay, parasitemia and infectivity
to triatomines by xenodiagnosis, and performed electrocardiography and
histology to assess myocardial damage and tissue pathology. Results Vaccination with TcVac1 elicited parasite-and antigen-specific IgM and IgG
(IgG2>IgG1) responses. Upon challenge infection, TcVac1-vaccinated dogs,
as compared to non-vaccinated controls dogs, responded to T.
cruzi with a rapid expansion of antibody response, moderately
enhanced CD8+ T cell proliferation and IFN-γ production,
and suppression of phagocytes’ activity evidenced by decreased
myeloperoxidase and nitrite levels. Subsequently, vaccinated dogs controlled
the acute parasitemia by day 37 pi (44 dpi in non-vaccinated dogs), and
exhibited a moderate decline in infectivity to triatomines. TcVac1-immunized
dogs did not control the myocardial parasite burden and electrocardiographic
and histopatholgic cardiac alterations that are the hallmarks of acute
Chagas disease. During the chronic stage, TcVac1-vaccinated dogs exhibited a
moderate decline in cardiac alterations determined by EKG and
anatomo-/histo-pathological analysis while
chronically-infected/non-vaccinated dogs continued to exhibit severe EKG
alterations. Conclusions Overall, these results demonstrated that TcVac1 provided a partial resistance
to T. cruzi infection and Chagas disease, and provide an
impetus to improve the vaccination strategy against Chagas disease. Immunization of dogs with DNA-prime/DNA-boost vaccine (TcVac1) enhanced the
Trypanosoma cruzi-specific type 1 antibody and
CD8+ T cell responses that resulted in an early control of
acute parasitemia and a moderate decline in pathological symptoms during chronic
phase. Further improvement of vaccine-induced immunity would be required to
achieve clinical and epidemiological benefits and prevent transmission of
parasites from vaccinated/infected dogs to triatomines.
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Risk factors associated with triatomines and its infection with Trypanosoma cruzi in rural communities from the southern region of the State of Mexico, Mexico. Am J Trop Med Hyg 2010; 82:49-54. [PMID: 20064995 DOI: 10.4269/ajtmh.2010.08-0624] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Trypanosoma cruzi prevalence in triatomines and risk factors associated to the presence of the insect were studied in 990 rural houses in the southern region of the State of Mexico, Mexico. In each house, triatomines were collected, and information related to house construction material was obtained. T. cruzi infection was diagnosed in all triatomines. A primary screening was performed using 2 x 2 contingency tables of exposure variables. All variables with P <or= 0.20 were analyzed by logistic regression. Triatomines (N = 125) were collected from 822 houses and analyzed for T. cruzi infection. Triatoma pallidipennis (97.4%) and Triatoma dimidiata (2.6%) were identified in 52.1% of the localities and in 6.1% of the houses. Infection was found in 28.0% of triatomines, from which 28.9% were nymphs. Factors associated with triatomine infestation were flooring construction material (dirt floor: odds ratio [OR], 10.05; 95% confidence interval [CI], 5.31-18.04; P = 0.0001), house rooms (at least three rooms: OR, 2.04; 95% CI, 1.07-3.86; P = 0.028), and ceiling construction material (cardboard lamina tile: OR, 6.84; 95% CI, 1.49-31.31; P = 0.013). This study shows T. cruzi circulation in triatomines in the area of study, and because triatomines are adapted for living and reproducing in the domestic environment, there is a potential risk of Chagas disease transmission to humans. Also, we can conclude that the construction materials and house inhabitants are risk factors of triatomines infestation.
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Trypanosoma cruzi circulating in the southern region of the State of Mexico (Zumpahuacan) are pathogenic: a dog model. Am J Trop Med Hyg 2009; 81:390-395. [PMID: 19706902 PMCID: PMC2784919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023] Open
Abstract
Here we describe clinical and pathologic evidence of Chagas disease caused in dogs by circulating Trypanosoma cruzi from a newly recognized endemic area in Mexico. We show that the Zumpahuacan isolate, although less virulent than the Sylvio-X10 reference strain that caused acute myocarditis and death, was pathogenic in dogs. Dogs infected with the Zumpahuacan isolate exhibited electrocardiographic alterations, left- and right-ventricle dilation, and hydropericardium. Histologically, diffused perimysial and endomysial lymphoplasmacytic cell infiltration, cardiomyocyte necrosis, and amastigote nests were noted in Zumpahuacan-infected dogs. These findings suggest that the risk of T. cruzi infection and Chagas disease is present in the State of Mexico, and further research is needed to identify the T. cruzi bio-types circulating in southern State of Mexico.
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Trypanosoma cruzi Circulating in the Southern Region of the State of Mexico (Zumpahuacan) Are Pathogenic: A Dog Model. Am J Trop Med Hyg 2009. [DOI: 10.4269/ajtmh.2009.81.390] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Sheep management and cryptosporidiosis in central Mexico. Trop Anim Health Prod 2008; 41:431-6. [PMID: 18679817 DOI: 10.1007/s11250-008-9208-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2007] [Accepted: 03/13/2008] [Indexed: 11/25/2022]
Abstract
To establish the association between sheep farm management practices and cryptosporidiosis in Central Mexico, 37 farms were invited and questionnaires answered by owners. Faeces samples were taken from lambs under 3 months old and ewes in the farms. Parasites were identified by modified Ziehl-Neelsen stain. Questionnaire included: general farm information, facilities characteristics, facilities cleaning measures, water use and farm and animal management practices. Farms were grouped in a low ( Pound 3,37%), medium (3.38-49.9%) and high basis ((3)50%) according to prevalence. Associations (OR) were calculated according to positivity, compared by chi-square test. A general prevalence of 34,33% was found. Five variables showed statistical significance (p<0.05). Associations found were: use of bed, grazing place, and bottle cleaning. The only association found between management practices and cryptosporidiosis that could represent a risk was the grazing place. This report is the first one in the country regarding predisposing conditions for cryptosporidiosis.
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GyrA
gene mutations and fluoroquinolone resistance in Salmonella
isolates from pigs in central Mexico. Vet Rec 2007; 160:630-2. [PMID: 17483384 DOI: 10.1136/vr.160.18.630] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Rat embryo quality and production efficiency are dependent on gonadotrophin dose in superovulatory treatments. Lab Anim 2006; 40:87-95. [PMID: 16460593 DOI: 10.1258/002367706775404471] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The present study was performed to optimize a superovulation protocol in rats in order to produce a large number of good-quality embryos suitable to develop rat embryonic stem (rES) cells. We first evaluated the ovulation kinetics of three rat strains: Wistar, Fisher and ACI/N. Animals (n=30 per strain) were treated with 50 IU of pregnant mare serum gonadotrophin (PMSG), and ovulation was induced with 50 IU of human chorionic gonadotrophin (hCG) 50 h apart. Next, we evaluated the dose-response curves of PMSG and hCG in Wistar rats in order to obtain the highest number of embryos. The parameters evaluated for superovulation efficiency were: percentage of mated females, percentage of pregnant females and the average number of embryos collected per female. The results of these experiments suggested that the best dose combination was 50 IU for each hormone. Subsequent experiments, again with Wistar rats, were designed to test which of four hormonal combination treatments (30/30, 30/50, 50/30, and 50/50 IU of PMSG/hCG) will produce the largest numbers of good-quality embryos. Embryo quality was evaluated by embryo development uniformity, embryo morphology, embryo survival in an in vitro culture and embryo ability to generate rES-like cells. Results from these experiments showed that 30/50 IU of PMSG/hCG was the treatment that induced the best embryo quality. In conclusion, our results indicated that, in Wistar rats, the most appropriate hormonal combination dose for superovulation protocols with high number of good-quality embryos was 30 IU of PMSG and 50 IU of hCG given 50 h apart. We are performing further studies with rES-like cells produced with the present methodology to evaluate if they are able to participate in the production of germ-line chimeras.
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Abstract
To determine Cryptosporidium spp. prevalence in faeces from asymptomatic sheep, 37 family flocks in Mexico State were sampled. Data were collected by the interview method and Ziehl-Neelsen stain of faecal samples for Cryptosporidium identification. The independent group proportion hypothesis test was used for differences in prevalences between sheep farms. A 34.3% general prevalence was found, and prevalence in herds with >100 animals was significantly higher (40.6%). Correlation was found between flock size and Cryptosporidium spp. presence (odds ratio, OR, 2.57; confidence interval, IC(95%), 1.84-3.60).
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