First molecular evidence of Toxoplasma gondii in opossums (Didelphis virginiana) from Yucatan, Mexico

Toxoplasma gondii is an obligate intracellular parasite recognized as a causal agent of toxoplasmosis; zoonotic disease endemic in many countries worldwide, including Mexico. Different species of animals participate in the wild cycle infection, including opossums of the species Didelphis virginiana. Thirteen D. virginiana were captured in Yucatan, Mexico. Detection of T. gondii was achieved by Polymerase Chain Reaction, which determined an infection of 76.9% (10/13) in brains. Positive amplicons were sequenced for analysis, this produced results similar to T. gondii with identity and coverage values of 98% and 96-100%, respectively. This study presents the first molecular evidence of the circulation of T. gondii in D. virginiana from Mexico.

Antigenic and genomic diversity of human rotavirus VP4 in two consecutive epidemic seasons in Mexico

In the present investigation we characterized the antigenic diversity of the VP4 and VP7 proteins in 309 and 261 human rotavirus strains isolated during two consecutive epidemic seasons, respectively, in three different regions of Mexico. G3 was found to be the prevalent VP7 serotype during the first year, being superseded by serotype G1 strains during the second season. To antigenically characterize the VP4 protein of the strains isolated, we used five neutralizing monoclonal antibodies (MAbs) which showed specificity for VP4 serotypes P1A, P1B, and P2 in earlier studies. Eight different patterns of reactivity with these MAbs were found, and the prevalence of three of these patterns varied from one season to the next. The P genotype of a subset of 52 samples was determined by PCR. Among the strains characterized as genotype P[4] and P[8] there were three and five different VP4 MAb reactivity patterns, respectively, indicating that the diversity of neutralization epitopes in VP4 is greater than that previously appreciated by the genomic typing methods.

Serotype specificity of the neutralizing-antibody response induced by the individual surface proteins of rotavirus in natural infections of young children

The relative contribution of the rotavirus surface proteins, VP4 and VP7, to the induction of homotypic as well as heterotypic neutralizing antibodies (NtAbs) in natural infections was studied. The NtAb titers of paired sera from 70 infants with serologically defined primary rotavirus infections were determined with a panel of rotavirus reassortants having one surface protein from a human rotavirus (serotypes G1 to G4 for VP7 and P1A and P1B for VP4) and the other surface protein from a heterologous animal rotavirus strain. A subset of 37 children were evaluated for epitope-specific antibodies to the two proteins by an epitope-blocking assay. The infants were found to seroconvert more frequently to VP4 than to VP7 by both methods, although the titers of the seroconverters were higher to VP7 than to VP4. Both proteins induced homotypic as well as heterotypic NtAbs. G1 VP7 frequently induced a response to both G1 and G3 VP7s, while G3 VP7 and P1A VP4 induced mostly homotypic responses.

[Frequency of serotype G rotavirus isolated from children with diarrhea in Mérida, Yucatán, Mexico]

During a period of six years (1985-1990), rotavirus G serotypes were investigated in 104 fecal samples isolates according to an immune enzyme assay using specific monoclonal antibodies against serotypes 1, 2, 3, and 4 of the VP7. The serotypes were established in 65 samples (62.5%) and could not be determined in 39 samples. In the 65 classified serotypes, 7 (6.7%) were found to belong to serotype 1, 23 (22.1%) to serotype 2, 12 (11.5%) to serotype 3, and 23 (22.1%) to serotype 4. The occurrence of the four serotypes during the six years was: serotype 3 was present in three of the six years; serotype 2 was detected in two epidemic outbreaks (1989 and 1990); serotype 3 appeared in the second year and was seen in the remainder of the study; and serotype 4 was present in the six years. We conclude that the four serotypes occur in our population and that future efforts to test the efficacy of any vaccine against this virus should evaluate a protective response against the four serotypes.

[Heterosexual transmission of the type I human inmmunodeficiency virus in a group of couples residing in the Yucatán peninsula]

OBJECTIVE

To ascertain the prevalence of type 1 human immunodeficiency virus (HIV-1) and to examine the factors associated with its transmission in a group of heterosexual couples.

DESIGN

Prospective study, descriptive, from September 1985 to December 1989. SITE. A university research center and a private general hospital in the city of Merida, State of Yucatan.

PATIENTS

Twenty-one adult patients (17 men and four women) with initial diagnosis of HIV-1 infection and their respective spouses. All the subjects were residents of the Yucatan peninsula.

INTERVENTIONS

The diagnosis of HIV-1 infection was made by the detection of antibodies against HIV-1 (by ELISA and Western Blot). Both the HIV-1 infection and the stage of AIDS were defined by the CDC criteria. The following factors were evaluated in order to define whether any were associated with the risk of transmission of HIV-1: marital status, time of marital status, type of sexual practices, average number of episodes of sexual intercourse per month, stage of HIV-1 infection of the case, presence of sexually transmitted diseases, and presence of genital ulcers.

RESULTS

Bisexuality was documented in 15 of the 17 males, and in two heterosexual relations with prostitutes was found. The female cases were infected by transfusion (two cases), intravenous drug addiction (one case) and prostitution (one case). Seventeen cases (81%) fulfilled the criteria for AIDS with diagnosis of HIV-1 infection HIV-1 was detected in eight out of 17 female spouses (47%) but not in the four male spouses. No relation was found between the variables and HIV-1 infection.

CONCLUSIONS

The presence of heterosexual transmission of HIV-1 in this study was 38%. The absence of associated factors suggests that heterosexual relations with an infected subject is sufficient for the transmission of HIV-1 to occur. The limited number of female cases makes it difficult to evaluate the efficiency of female-male transmission. Bisexual practices were the predominant cause of HIV-1 infection in the male cases, and as a consequence, the indirect cause of HIV infection in the female spouses.

Role of rotavirus and enteric adenovirus in acute paediatric diarrhoea at an urban hospital in Mexico

Of 150 acute diarrhoea paediatric cases admitted to the General Hospital Augustín O'Horán in Mérida, Yucatán, México between January 1986 and December 1986, human rotavirus was detected in the faeces of 48 (32%) either as the sole aetiological agent or in association with other viruses. Adenovirus was detected in faeces of 18 (12%) patients. Rotavirus of the long pattern type (antigenic subgroup II) predominated. Children aged 7 to 12 months were most commonly infected. Rotavirus was detected throughout the year, whereas adenovirus was detected between January and September only. Clinical features of patients with rotavirus and adenovirus infections are compared.

[Acute infantile diarrhea caused by rotavirus in a pediatric population of Mérida, Yucatan, Mexico]

The frequency and clinical characteristics of rotavirus infections were studied in 150 infants hospitalized in the General Hospital "Agustin O'Horán" SSA in Mérida, Yucatán, México, because of acute gastroenteritis during 1986. Rotavirus was detected in 32% of all subjects tested. Rotavirus was detected in all months studied. An age-related incidence peak was observed between 7 and 24 months and the infection proved to prevail within the rural area. The clinical pictures were analyzed. We consider it necessary to carry out many more studies in our country in order to obtain reliable knowledge of this problem.

[Infection caused by rotavirus in children hospitalized because of gastroenteritis in Yucatan, Mexico]

A one year study was performed in patients hospitalized by gastroenteritis. The purpose of this study was to determine the rate of gastroenteritis by rotavirus, as well as which subgroups and electropherotypes are the prevailing ones. Electrophoresis technique in polyacrylamide gel was used to detect ribonucleic acid of rotavirus directly obtained from feces. Results indicated that rotavirus was the cause of gastroenteritis in 28.8% of the patients studied; prevailing subgroup II. Four electropherotypes of 34 virus isolated were detected, unlike other countries where have been isolated 19 virus.

Prevalent patterns of serotype-specific seroconversion in Mexican children infected with rotavirus

The level of neutralizing antibodies to rotaviruses belonging to serotypes 1, 3, and 4 was determined in acute- and convalescent-phase sera from 36 Mexican children with rotaviral diarrhea. Most of the infants who seroconverted fell into one of the following three patterns: single seroconversion to serotype 1; seroconversion to serotypes 1 and 4; or seroconversion to all three serotypes tested. The heterotypic neutralizing antibody responses to rotavirus infections are discussed.