Timothy P. Hughes

Genetic susceptibility to cholera

In the course of studies of immunity to experimental cholera in man, 10(5) or 10(6) Vibrio cholerae were given to 66 college students and other community volunteers under quarantine in an isolation ward. HLA antigen and blood group determinations were carried out to test the hypothesis that severity of clinical cholera is dependent in part upon genetically-determined host susceptibility. Fifty-five volunteers developed diarrhoea; 38 had mild illness and 17 had severe cholera (stool volume greater than or equal to 5.0 litres). HLA antigens were found in similar frequency in volunteers with severe, mild or no diarrhoea; antigen A1, A2, A3 and B7 were most common. Blood group O, however, was found in 64% of persons with severe cholera versus 36-38% of volunteers with mild or absent illness. Thus, while no correlation was found between HLA type and severity of cholera, these results do support the claims of other investigators that blood group O is found more frequently in patients with severe cholera than in the normal population.

CANNABIS, HYPOCHLORHYDRIA, AND CHOLERA

In 90 volunteers participating in a vaccine-development programme consumption of beer more than 3 days a week was linked with high stomach acid output, and smoking of cannabis greater than 2 days a week was linked with low acid output. In 92 volunteers challenged with Vibrio cholerae or enterotoxigenic Escherichia coli, heavy use of cannabis was associated with more voluminous diarrhoea. Cannabis use may be an important factor predisposing to severe diarrhoea.

Association between O blood group and occurrence and severity of diarrhoea due to Escherichia coli

During studies of diarrhoea due to Escherichia coli in 316 adult volunteers, ABO and Rh blood group determinations were done to look for differences in the occurrence or severity of illness in association with certain blood groups. In studies using heat-labile enterotoxin-producing E. coli, volunteers with O blood group had a significantly higher attack rate for diarrhoea than persons with other blood groups. In contrast, in studies with enteropathogenic or heat-stable enterotoxin-producing E. coli, no association was found between occurrence of diarrhoea and ABO group. These studies, and previous studies finding a similarly increased susceptibility to cholera in persons with O blood group, suggest that the mechanism of increased risk involves an interaction between blood group substances and the similar enterotoxin produced by E. coli and Vibrio cholerae.

Variability of sodium and sucrose levels of simple sugar/salt oral rehydration solutions prepared under optimal and field conditions

5 nurses and 14 Honduran mothers made up oral rehydration solutions from available materials (nurses bought supplies in Baltimore stores and Hondurans were supplied sugar and water by a rural health center but were asked to bring their own measuring devices) to determine the accuracy of homemade solutions under optimal and field conditions. 3 methods of preparation were used: 1) pinch and scoop; 2) household teaspoon and glass (both nurses and Honduran mothers performed these) 2; and 3) special double-ended plastic spoons (nurses only). The solutions prepared by the 5 U. S. nurses familiar with the physiologic basis of oral therapy and skilled in its use represent optimal conditions. However, there were statistically significant (P .01) nurse-to-nurse sodium level variations using Methods 1 and 2, making these methods unsuitable for promotion in an oral therapy program without health worker supervision. The findings from the Honduran mothers corroborated these findings (and others) because their sodium levels were generally beyond acceptable levels. Therefore, the special double-edged spoon method should be evaluated for its adaptability to field conditions.

Immunogenicity and reactogenicity of lowered doses of rhesus rotavirus vaccine strain MMU 18006 in young children

Rhesus rotavirus oral vaccine strain MMU 18006 at a dose of 10(5) plaque-forming units (PFU), a 1:10 dilution of the original undiluted vaccine, is highly immunogenic in young children. Fevers have occurred, however, on Days 3 and 4 following vaccination. This study was conducted to determine whether febrile reactions could be eliminated and immunogenicity maintained by (1) giving smaller doses of vaccine or (2) vaccinating younger infants. Thirty-one children between 3 and 11 months of age received, in a randomized, double blind manner, either 10(4) PFU of vaccine virus, 10(3) PFU of vaccine virus or placebo. All recipients of the 10(4) PFU dose had a seroresponse; however, some degree of immunogenicity was lost with the smaller dose (10(3) PFU). Fevers were observed in recipients of both of the lowered doses of vaccine but the febrile reactions were related to the age of the vaccinee. No infant younger than 5 months of age experienced a temperature elevation, whereas the majority of children older than 5 months had fevers. Our data suggest that the lack of reaction in the younger infants correlates with the presence of prevaccination neutralizing antibody, presumably transplacentally acquired. We conclude that the rhesus rotavirus oral vaccine at a dose of 10(4) PFU is immunogenic and appears to be safe in young infants.

POTASSIUM SUPPLEMENTS FOR ORAL DIARRHŒA REGIMENS

A study is proposed for supplementing potassium loss from diarrhea in rehydration therapies with fresh fruit and other naturally potassium-rich foods. Bananas contain .1 mol of potassium per gm. Freshly squeezed lemon or orange juices were tested for potassium and sodium content and found to have very low potassium concentration. Therefore, the banana was chosen for an upcoming study that will determine if infants and children suffering from diarrhea can ingest the amounts of the fruit necessary to elevate the potassium level sufficiently. Bananas as the potassium source are thought to be well-accepted in developing areas.