Michael T Ashcroft

A SEVEN-YEAR FIELD TRIAL OF TWO TYPHOID VACCINES IN GUYANA

Abstract In 1960 about 72,000 Guyanese schoolchildren, aged five to fifteen years, were divided into three similar groups, one of which acted as a control and was given tetanus toxoid, the second was given an acetone-killed typhoid vaccine, and the third a heat-killed-phenolised typhoid vaccine. Two subcutaneous doses of 0.5 ml. of reconstituted vaccines were given five weeks apart. An additional 10,000 children received one dose only. The incidence of typhoid fever, diagnosed by the bacteriological isolation of Salmonella typhi , was followed for seven years after vaccination. In those given two doses, 146 cases of typhoid occurred in the control group and 16 and 49 in the acetone and heat-phenol typhoid vaccine groups, showing protection-rates of 88% and 65%, respectively. In those given one dose of vaccine the protection was somewhat greater, 22 cases occurring in the control group and 1 and 4 in the groups given the acetone and heat-phenol vaccines, respectively. Protection showed little diminution until the fifth year after vaccination.

The Clinical Features of Sickle-Cell/β Thalassaemia in Jamaica

The clinical and haematological features of 56 Jamaican patients with sickle‐cell /β‐thalassaemia (S/Thal) are reviewed. The two types of S/Thal (with and without Hb A) had distinctive haematological and clinical characteristics. In general, the non‐Hb‐A type had evidence of lower haemoglobin levels, a more rapid haemolytic rate, and a more severe clinical course than the Hb‐A type.

The Clinical Features of Haemoglobin SC Disease in Jamaica

Summary. The clinical and haematological features of 90 Jamaican patients with haemoglobin SC disease are reviewed. Mean haemoglobin levels indicated mild anaemia although individual haemoglobin levels were often within the normal range. The clinical features were qualitatively similar to those of homozygous sickle cell disease (SS disease) although they were generally less frequent and of lesser severity. Ocular pathology was an exception, occurring more frequently in SC disease than in SS disease even in age–sex‐matched groups. There is some evidence that the higher haemoglobin level in SC disease may be aetiologically related to retinal vascular disease.

Mortality and morbidity in Jamaican adults with sickle-cell trait and with normal haemoglobin followed up for twelve years.

An epidemiological survey of adults aged 35--64 years living in a rural area of Jamaica was started in 1962--63 and continued until 1975. Information was available on 856 subjects with AA and 119 subjects with AS haemoglobin genotypes. The mortality-rates over 12 or 13 years and the number of clinic attendances in 10 years did not differ significantly between subjects with AA and those with AS haemoglobin. The patterns of disease as well as the life expectancy of the two groups appeared to be the same.

BLOOD-PRESSURE AND MORTALITY IN A RURAL JAMAICAN COMMUNITY

1065 men and women aged 35--64 years living in rural Jamaica were first examined in 1962--1963, re-examined 5 and 10 years later, and followed-up until 1976. Overall mortality in 13 years, taking into account blood-pressures at all 3 surveys, showed that mortality was significantly increased only at pressures above 180 mm Hg systolic or 110 mm Hg diastolic. It was estimated that without this degree of hypertension the total number of deaths between the ages of 45 and 69 years would have been reduced by about 17%. Unlike other reports, mortality showed no significant association with lower levels of blood-pressure; this difference may be due to a lower incidence in this community of coronary and cerebral thrombosis. The relation between blood-pressure and mortality cannot be assumed to be identical in populations with different profiles of cardiovascular pathology.

Haemoglobin concentration, eosinophilia and intestinal helminths in children in rural Jamaica.

Abstract Investigations on haemoglobin and haematocrit values, eosinophils and faecal helminth eggs in rural Jamaican infants and children are summarized. Haemoglobin levels rose from 10·6 g.% at about the fifth month of life to 10·9 g.% at one year and thereafter climbed slowly to 12·2 g.% at 6 years and remained at this level to 15 years. Values for haematocrit and MCHC behaved similarly. The mean haemoglobin levels were about 1·0 g.% below optimal values but about 2·0 g.% above those reported from Gambia. Severe anaemia was rare but minor degrees of iron deficiency and, in the first year of life, of folic acid deficiency, may be common. 2 cases of sickle-cell anaemia and one of thalassaemia major were seen. Neither malaria, which has been eradicated, nor hookworm is now an important cause of anaemia in Jamaica. Helminth eggs in stools were not common in the first and second years but were present in 60% of children in the third and fourth years. Ascaris lumbricoides was the most prevalent, giving rise to the heaviest concentration of eggs, followed by Trichuris trichiura . A few hookworm eggs were found in about 10% of children over 2 years. In one study involving 160 children aged about 3 years, no relationship was found between helminth eggs and haemoglobin levels, heights, weights or symptoms which might be related to infection. Helminthiasis, although extremely common, does not appear to be a major cause of ill-health or of failure to thrive among Jamaican children. Eosinophils were numerous in the latter half of the second year of life and by 5 years, on average, comprised 13·5% of all white cells. Although an aetiology other than intestinal helminthiasis is not obvious, a correlation between eosinophils and faecal helminth eggs could not be demonstrated. Some children may have been infected with Toxocara canis .

Ethnic differences in growth potential of children of African, Indian, Chinese and European origin

Community surveys of infants and children of African, Indian, Chinese and European origin in Guyana and Jamaica have been reviewed in order to compare the influence of ethnic origin and environment, including nutrition, on anthropometric measurements used to assess nutritional status. Mean heights and weights of African and European were greater than those of Indian and Chinese children. African had greater weight for height and greater arm circumferences but smaller triceps skinfolds than Indian children. These differences, which cannot be explained by nutritional or other environmental causes, show that ethnic origins cannot be disregarded when assessing nutritional status by anthropometric measurements. Specific adjustments to international standards of height and weight are proposed in order to make them more appropriate for Indian and Chinese children.

A comparison of T-wave inversion, S-T elevation, and RS amplitudes in precordial leads of Africans and Indians in Guyana

Abstract ECG precordial leads of 830 Guyanese men and women of African and Indian origin, aged 35 to 54 years, were compared. The prevalence of nonupright T waves in right precordial leads (V 1 to V 3 ) were similar in the two ethnic groups. T-wave inversion in V 1 , V 2 , and V 3 was present in 46.4 per cent, 3.5 per cent, and 2.4 per cent of women, respectively, compared with 9.6 per cent in V 1 and no inversion in V 2 and V 3 in men. S-T elevation occurring in any of the precordial leads was present in 2.1 per cent of African women, 0.9 per cent of Indian women, 18.1 per cent of African men, and 13.6 per cent of Indian men. Neither T-wave inversion in right precordial leads nor S-T elevation were associated with detectable clinical abnormality, hypertension, obesity, or raised blood cholesterol levels and both appeared to be normal variants. S-T elevation was associated with large QRS complexes. Mean amplitudes of S waves in V 1 and R waves in V 5 and V 6 were significantly greater in men than in women and in Africans than Indians. These differences could only be partially explained by variations in age, blood pressure, obesity, or cardiothoracic ratios. Possible ethnic and sex differences in the prevalence of T-wave inversion in right precordial leads, S-T elevation, and high amplitude QRS complexes can be of clinical and epidemiological importance.

Growth of Guyanese infants of African and East Indian racial origins, with some observations on mortality☆

Abstract Mean weights at various intervals over the first 2 years of life were calculated for Guyanese infants of East Indian and African ethnic groups who were born in 1964 and attended 14 clinics in rural areas. Compared with East Indians, African infants grew faster and weighed more at all ages, although their mortality experience was greater. It is suggested that Africans have a greater potential size than East Indians as a result of inherited factors. Compared with results from developed countries, weight increments in both ethnic groups were small from the 4th to 15th month, a time when mortality was relatively high. This growth pattern is found in many developing countries and reflects weaning difficulties. Profound changes in population, mortality rates and birth rates occurring in Guyana over the past century are summarized.

Treponemal serological tests in Jamaican school children

Abstract Yaws, although occurring in parts of Jamaica, is much rarer than in the past. Sera from children, 7–15 years old, attending primary schools in areas in which the incidence of yaws differs, were examined by the VDRL and RPCF tests. The proportion reactive at the schools ranged from 1·6% to 27·6% and 4·0% to 34·1% respectively. Clinical yaws was seen in only one of the sero-reactors; most of the other positive tests were in children with either latent or cured yaws. It is suggested that the RPCF, which showed a higher proportion of reactors than the VDRL test, measures antibodies against yaws different from those measured by the VDRL test in these circumstances. The immediate and long-term problems of sero-reactivity in a country where both yaws and syphilis are present are discussed.