Biomedical subjects
Publications and source records attributed to C C Draper.
An outbreak of Plasmodium malariae malaria occurred in Grenada some 16 years after the end of a malaria eradication campaign, probably due to renewal of transmission from recrudescent cases. Serological studies were used in addition to blood film surveys in defining the outbreak, and their value in such surveillance situations is emphasized.
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In five rhesus monkeys surviving 'Peru strain' or 'strain 7' Trypanosoma cruzi infection for six to eight years, positive xenodiagnosis results and high indirect fluorescent antibody titres (4096 - 65536) persisted until the animals were killed. Abnormal electrocardiograph patterns in two monkeys (H and K) were possibly compatible with myocardial damage. Histopathological changes attributable to T. cruzi infection were minor in four monkeys but severe in one (R). In this animal, infected with what was judged previously to be the less virulent of the two T. cruzi stocks used ('strain 7'), there was severe myocarditis, with myofibre degeneration, and lesions of the oesophagus. Elevated serum levels of five enzymes were not detected in any of the chronically infected monkeys.
A total of 1,197 wild animals from Pará State north Brazil, were examined for haematozoa. Trypanosoma cruzi-like parasites were found in 13 different species, and were particularly common in a variety of marsupials (Didelphidae), porcupines (Coendou spp.), armadillos (Dasypus novemcinctus) and coatimundis(Nasua nasua). Three human infections are reported, making a total of seven autochthonous cases of Chagas's disease from Pará since the first were described in 1969. A serological survey of 5,319 inhabitants from the Belém suburbs revealed 14 positive reactions with immunofluorescent antibody titres greater than 1:64, and 15 equivocal reactions at 1:16. No evidence was found of silvatic species of triatomine bugs (Hemiptera: Reduviidae) colonizing houses, but occasional infected specimens of Panstrongylus geniculatus and Rhodnius pictipes were found in suburban houses, near the forest. Human infection is considered to be silvatic in origin. Chagas's disease could become endemic in the Amazon Basin if silvatic triatomine bugs were able to adapt to a domestic habitat: the real danger, however, is in the possible importation of already domiciliated vector-species along the newly opened highways, from other endemic regions of Brazil. Other Trypanosoma species were recorded in a variety of wild animals. Haemogregarines were found in some marsupials and rodents, and piroplasms in marsupials and a single armadillo.
Sixty-one serum samples selected on the basis of reactivity in the complement fixation (CF) and latex agglutination (LA) test, were further examined for sensitivity and specificity by indirect haemagglutination (IHA), enzyme linked immunosorbent assay (ELISA) and defined antigen substrate spheres (DASS). Twenty sera from healthy Europeans and 48 samples from patients with either schistosomiasis or trichinosis were also tested. Comparable levels of sensitivity were found between the CF and LA positive sera and IHA, ELISA and DASS. Of the CF positive LA negative group of sera, many were positive by DASS but only a few reacted in IHA and ELISA. Some cross reactivity was also observed in the schistosomiasis sera tested by IHA and ELISA.
Extensive studies of the use of the ELISA test for the detection of antibodies in Schistosoma mansoni infections are described. A method has been evolved for the determination of the optimum value for the reference serum endpoint. In chimpanzees infected with S. mansoni a crude egg antigen detected antibodies earlier in the infection than did a worm antigen and was generally more reactive. The ELISA test, using the egg antigen, has been applied to sera from populations infected with S. mansoni, with other human schistosomes, or with helminth infections other than schistosomiasis. The ELISA test was as sensitive as the IFAT and CFT, but more specific. However, many cross-reactions occurred in infections with other human (and with animal) schistosomes, although to a lesser extent with other helminths. In surveys in the Sudan the use of blood collected on absorbent paper was only slightly less sensitive for the detection of antibodies than sera, and this technique showed that the prevalence of infection was higher than that measured by stool examination alone. Possible future developments are discussed with a view to improving sensitivity and specificity both for clinical and epidemiological work.
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Household distribution of seroreactivity to Trypanosoma cruzi in inhabitants was analyzed in relation to house construction and the distribution of Panstrongylus megistus, the principal domestic vector of Chagas' disease in a rural area in northeast Brazil. No children residing in mud-brick houses were seroreactive to T. cruzi. The highest rates of seroreactivity occurred in residents of unplastered mud-stick houses, and were twice as high as those found in persons living in mud-brick houses or plastered mud-stick houses. Two-thirds of seroreactive children in this area resided in unplastered mud-stick houses. Over 90% of the P. megistus infestations were found in mud-stick houses. Mud-brick houses had the lowest infestation rates of P. megistus and the lowest household rates of seroreactivity to T. cruzi.
The prevalence of Trypanosoma cruzi parasitemia as determined by xenodiagnosis on domestic dogs and cats was correlated with household rates of seroreactivity to T. cruzi and household Panstrongylus megistus infestation in a rural area in northeast Brazil where P. megistus was the only domiciliary triatomine vector. T. cruzi infection was present in about 18% of domestic dogs and cats. Two-thirds of seroreactive children below age 10 resided in houses with T. cruzi-infected animals. In houses with a T. cruzi-infected dog or cat, as well as at least one infected P. megistus, the household rate of seroreactivity to T. cruzi was five times greater than in houses with non-infected domestic animals and no infected triatomine vectors. Domestic dogs and cats are important reservoirs of T. cruzi in an endemic area where P. megistus is the only domiciliary triatomine vector.
The development of hepatosplenic schistosomiasis in humans cannot always be related to the intensity of infection. A study was designed to identify different humoral immunologic responses to Schistosoma mansoni in patients with and without hepatosplenic disease. Twenty-four patients with active hepatosplenic disease were closely matched for age, sex, and fecal egg counts with twenty-four patients with only intestinal disease. A serum sample from each of these patients was tested for antibodies to the major soluble egg antigen (MSA1) by radioimmunoassay, for total and IgM antibodies to egg and worm antigenic preparations by ELISA, and for its ability to suppress antigen stimulated lymphocyte blastogenesis. No difference was found using these assays between the hepatosplenic and the intestinal schistosomiasis patients.
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Information on the acute and early chronic phases of infection with Trypanosoma cruzi in eight rhesus monkeys is reported with particular reference to the pattern of subpatent parasitaemia and serology. Xenodiagnosis was superior to animal inoculation and blood culture in its capacity to detect subpatent parasitaemia. Each monkey showed an individual, relatively constant pattern of this not related to the nature of the inoculum. Levels of indirect fluorescent and indirect haemagglutinating antibodies remained elevated during a year of observations. One monkey died with a megaoesophagus. Another monkey after challenge with a heterologous strain by orbital inoculation failed to develop Romana's sign and showed no change in serum antibody levels or degree of xenopositivity.
The North Korean strain of Plasmodium vivax was characterized by its extraordinarily prolonged incubation period in certain circumstances. It was clearly demonstrated by quantitative observations that the phenomenon may be elicited by the inoculation of small numbers of sporozoites. After the intradermal inoculation of 10 or 100 sporozoites, the incubation period was delayed for periods varying between 262 and 628 days; after u,000 sporozoites, with one exception, the same delay occurred; after 100,000 sporozoites, the incubation period was always of normal duration (13--16 days). Two laboratory-acquired infections in workers who had taken a prophylactic drug showed incubation periods of 315 and 329 days, respectively. Various theories for the phenomenon of prolonged prepatent periods are examined, and the most satisfactory one is based on the presumed existence of two populations of sporozoites in P. vivax. In temperate strains, sporozoites requiring long prepatent periods (LPP) for development are present in great excess over a much smaller proportion of sporozoites characterized by short prepatent periods (SPP); thus small doses will elicit the phenomenon, though doses of over 1,000 sporozoites will mask the effect as the few SPP sporozoites will produce an infection with a normal (i.e. short) prepatent period. In tropical strains, the relative proportions are different, perhaps in equal numbers, and even in small doses some SPP sporozoites will be present and normal prepatent periods should ensure whatever the dosage."
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The prevalence rates and household distribution of seroreactivity to Trypanosoma cruzi by complement fixation (CF) and indirect immunofluorescent antibody methods were determined in a population of 1,087 persons living in a rural area endemic for Chagas' disease in northeast Brazil. There was a gradual rise in the rate of seropositivity to 60% by age 20. Between ages 20 and 55 the prevalence rate remained at about 60%, but declined thereafter. The decline in the older age groups was not accompanied by a fall in geometric mean titer, suggesting that the decline might better be explained by an increased mortality among those seropositive than by a decrease in CF reactivity associated with age. There was variation in the rates of seropositivity in children among the geographic subunits, but the rates among adults were fairly uniform. Household clustering of seropositivity was demonstrated when both household size and age distribution were taken into account. The presence of a seropositive child less than 5 years of age was a good indicator of a household with a high rate of seropositivity; screening for young seropositive children might be a useful tool to locate high risk households. Seropositive children in households where the mother was seropositive but the father seronegative were significantly younger than seropositive children in households where the father was seropositive but the mother seronegative even though the age distribution and the overall rate of seropositivity in both groups of children were similar; thus, conversion to seropositivity earlier in life in children of seropositive mothers may not be due solely to increased exposure, but may indicate that the immunologic response in such children differed from that of children from seronegative mothers.
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A survey for schistosomiasis in a village in the Gezira area of the Sudan in 1973 showed that there has probably been a great increase in the incidence of S. mansoni infection in the last 25 years. Severe morbidity was uncommon in this sample but overt infection was associated with the symptoms of bloody diarrhoea, tiredness, and possibly abdominal pain, and with a reduced level of haemoglobin. Hepatosplenomegaly was common and schistosomiasis is considered to have contributed to this, although hyperendemic malaria must also have been important in its causation.
Immune complexes have been detected in the sera of people infected Schistosoma mansoni by the technique of acidification followed by double countercurrent immunoelectrophoresis in hypertonic buffered gels.