Direct and indirect estimates of HIV-1 incidence in a high prevalence population

While the worldwide AIDS epidemic continues to expand, directly measured incidence data are difficult to obtain. Methods to reliably estimate human immunodeficiency virus type 1 (HIV-1) incidence from more easily available data are particularly relevant in those parts of the world where prevalence is rising in heterosexually exposed populations. The authors set out to estimate HIV-1 incidence in a population of heterosexual sexually transmitted disease clinic attended in Trinidad who had a known high prevalence of HIV-1 subtype B. Over the period 1987-1995, HIV-1 incidence estimates from serial cross-sectional studies of HIV-1 prevalence, passive follow-up of clinic recidivists, modeling of early markers of HIV-1 infection (p24 antigen screening), and a cohort study of seronegative genital ulcer disease cases were compared. Measuring incidence density in the genital ulcer disease cases directly gave the highest estimate, 6.9 percent per annum. Screening for the detection of early HIV-1 markers yielded an incidence of 5.0 percent per annum, while estimating incidence from serial cross-sectional prevalence data and clinic recidivists gave estimates of 3.5 percent and 4.5 percent per annum, respectively. These results were found to be internally consistent. Indirect estimates of incidence based on prevalence data can give accurate surrogates of true incidence. Within limitations, even crude measures of incidence are robust enough for health planning and evaluation purposes. For planning vaccine efficacy trails, consistent conservative estimates may be used to evaluate population before targeting them to cohort studies(AU)

Congenital yellow fever virus infection after immunization in pregnancy

To determine whether yellow fever (YF) vaccine administered in pregnancy causes fetal infection, women who were vaccinated during unrecognized pregnancy in a mass campaign in Trinidad were studied retrospectively. Maternal and cord or infant blood were tested for IgM and neutralizing antibodies to YF virus, indicating congenital infection. The infant, the first repotred case of YF virus infection after immunization in prgnancy, was delivered after an uncomplicated full-term pregnancy and appeared normal. Congenital dengue 1 infection may have occurred in another case. The frequency of fetal infection and adverse events after such exposure could not be estimated; however, the neurotropism of YF virus for the developing nervous system and the now documented possibility of trans-placental infection underscores the admonition that YF vaccination in pregnancy should be avoided (AU)

Private sector response against the cholera treat in Trinidad and Tobago

During the first half of 1992 the threat of cholera to Trindad and Tobago prompted a strong health education effort by public authorities and the private sector. To help assess the private sector effort, the cost of cholera-related advertisements and private announcements placed in the country's two leading newspapers during January-June 1992 were received. The review indicated that an estimated TT$ 540 660 was spent on these ads and announcements, that they contributed strongly to keeping cholera prevention continuously in the public eye, and that most of the messages published were accurate, specific, and safe. The strength and success of the private contribution to cholera prevention in this case suggests that similar approaches could be applied to other health problems and to the cholera problem outside Trinidad and Tobago. Overall, the lesson appears to be that if one can find congruence between private sector motives and public health interests, then the potential prospects for a successful partnership are great (AU)

Immunologically determined prevalence rates of antibodies to toxocara canis in school children in Trinidad, West Indies - abstract

Preliminary observations of a high frequency of serum antibodies to Toxocara canis in patients attending Eye Clinic at the General Hospital, Port of Spain, Trinidad led to the hypothesis that children with pet dogs may have as high a frequency. Hence, the sera of 339 school children, randomly selected from the school register, were tested by ELISA for the presence of IgG and IgM antibodies to T. canis. The prevalence rate of T. canis antibodies in schoolchildren in Countries Victoria and St. Patrick (32.5 percent) were similar but higher than that in Country Caroni (12.7 percent). Overall, a prevalence rate for Trinidad was determined (77.6 percent) which was similar to that found in Dominica (78.9 percent), St. Kitts/Nevis (75.3 percent) and Grenada (78.5 percent). Apart from Toxocara, other helminths only, 12 had helminths and protozoan parasites and 26 had protozoan parasites only. Of 31/83 students without antibodies to T. canis, 7 had helminths only, 2 had helminths and protozoan parasites and 22 had protozoan parasites only (AU)

Blastocystis hominis in immunocompetent children in Trinidad - abstract

Blastocystis hominis, formerly described as an enteric yeast, was reclassified as a protozoan parasite. The organism has elicited tremendous interest as reports have been controversial regarding its status as a pathogen or non-pathogen. Between March and August, 1990, we examined the formed stools of 894 asymptomatic children (age range 1-14 years) by the modified Ritchie-formalin-ethylacetate method for ova and cysts of parasites. Fourteen of the 73 under-five (19.2 percent) had B. hominis with 8/10 having B.hominis only. Seventy-one of 96 (74 percent) orphans had parasites, 64 (66.7 percent) of whom had B.hominis with 22/64 (34.4 percent) having B.hominis only. In the survey sample of 705 school children 158 (22.4 percent) had parasites with 98 having B.hominis and 74/98 (75.55 percent) had B.hominis only. It was noted that 13 children who had heavy B.hominis burdens did not present with diarrhoea. Children 8-12 years old appeared to be most frequently colonised. From our experience, we conclude that B.hominis in immunocompetent children is not a pathogen (AU)

Surveillance and management of sylvatic yellow fever in Trinidad (1988-1989) - abstract

Howler monkey (Aloutta sp) deaths in the Southeastern forests of Trinidad were reported in December, 1988. This paper reports the laboratory and field investigations and preventive measures which were undertaken, in view of the known association between such deaths and yellow fever (YF) activity. A total of 47,640 adult mosquitoes were captured in several forest regions in Trinidad during the period December 1988 to October, 1989. Mosquitoes were identified, pooled and processed for virus isolation. Blood and organs from 5 dead Howler monkeys submitted between December 1988 and March, 1989 were examined for the presence of YF virus. Virus isolation was done by innoculation of material in AP61 (Ades pseudo-scutellaris) tissue culture and in 2-day-old Swiss albino mice, followed by identification of YF isolates by immunoflourescence, using monoclonal antibody and standard mouse neutralization tests, respectively. Fourty-four species of mosquito belonging to 14 genera were identified. From 654 mosquito pools, 6 YF isolates were obtained from only 2 species: five isolates from haemagogus janthinomys (December, 1988) and 1, for the first time locally, from Sabethes chloropterus (January, 1989). YF virus was isolated from blood and organs of 2 Howler monkeys captured on February 22 and March 2, 1989. There were no human cases of YF. Yellow fever activity appeared to be confined to the southeast part of the island. Preventive measures included mass targeted YF immunization (400,000 doses administered in 3 months), intensified vector control operations and reduced human contact with forest mosquitoes by the existing ban on hunting (AU)

Peregrine malaria and international travel: the Trinidad experience

Incidence of imported malaria, growth in the gross national product (GNP) and increases in international travel were correlated during 1966 to 1986 in Trinidad, W.I. A significant (P<0.05) relationship was found between imported malaria and business travel. However, it can be inferred that growth in GNP, resulted in increases in international travel (local and foreign). During this study an increase of over 314 percent in international travel was recorded. A total of 84 malaria cases was found, with 44 Plasmodium falciparum, 25 P. vivax, 11 P. malariae and 1 P. ovale. There were 3 cases of mixed infections, 2 of P. malariae and P. vivax in 1985 and 1 of P. malariae and P. ovale in 1980. It is recommended that active port surveillance should be maintained to handle present and future increases in international travel and their associated disease problems. (AU)

Serum cholinesterase levels of vector control workers in Trinidad, West Indies (1979-1982)

During the period 1979-1982, serum cholinesterase levels were determined in blood samples collected from workers employed at the Insect Vector Control Division, Trinidad, W.I. A total of 1,162 blood samples were collected, of which 116 showed suppressed cholinesterase levels. Those workers with low serum cholinesterase levels included 46 residual spraymen, 66 Aedes aegypti operators and 4 controls. The difference in numbers of spraymen and Aedes operators with low cholinesterase levels was significant (p<.001). No significant differences were found in the number of Aedes operators with low cholinesterase levels from North and South Trinidad. Similarly, no differences were found in the number of residual spraymen from North and South Trinidad with low cholinesterase levels. A total of 7 Aedes operators and 4 residual spraymen had persistently low serum cholinesterase levels. It is likely that the main areas of absorption were the hands and forearms, with further absorption occurring via respiration. The need for continuous monitoring and supervision of vector control workers who handle insecticides is stressed (AU)