Field and laboratory comparative evaluation of ten rapid malaria diagnostic tests.

The paper reports on a comparative evaluation of 10 rapid malaria tests available in South Africa in 1998: AccuCheck (AC, developmental), Cape Biotech (CB), ICT Malaria Pf (ICT1) and Pf/Pv (ICT2), Kat Medical (KAT), MakroMal (MM), OptiMAL (OP), ParaSight-F (PS), Quorum (Q), Determine-Malaria (DM). In a laboratory study, designed to test absolute detection limits, Plasmodium falciparum-infected blood was diluted with uninfected blood to known parasite concentrations ranging from 500 to 0.1 parasites per microlitre (P/microL). The 50% detection limits were: ICT1, 3.28; ICT2, 4.86; KAT, 6.36; MM, 9.37; CB, 11.42; DM, 12.40; Q, 16.98; PS, 20; AC, 31.15 and OP, 91.16 P/microL. A field study was carried out to test post-treatment specificity. Blood samples from malaria patients were tested with all products (except AC and DM) on the day of treatment and 3 and 7 days thereafter, against a gold standard of microscopy and polymerase chain reaction (PCR). OP and PS produced fewer false-positive results on day 7 (18 and 19%, respectively) than the other rapid tests (38-56%). However, microscopy, PCR, OP and PS disagreed largely as to which individuals remained positive. The tests were further compared with regard to general specificity, particularly cross-reactivity with rheumatoid factor, speed, simplicity, their ability to detect other species, storage requirements and general presentation.

In vitro sensitivity of southern African isolates of Plasmodium falciparum to halofantrine.

Twenty southern African isolates of Plasmodium falciparum and a 'control' Gambian strain were tested in vitro for their sensitivity to halofantrine. The concentration required to inhibit 50% of parasite growth, the IC50, ranged from 0.039 to 15.000 nmol/litre, with a mean of 4.619 nmol/litre. These IC50 values were comparable with those obtained in studies carried out in West Africa but were higher than the IC50 of South-East Asian isolates. All 21 isolates examined in the present study had minimum inhibitory concentrations (MIC) of 32 nmol/litre or less, with a median MIC value of 8 nmol/litre. Halofantrine was equally active against chloroquine-sensitive and chloroquine-resistant isolates and was also active against pyrimethamine-resistant strains. Indications are that this drug would be suitable for the treatment of P. falciparum malaria in the southern African region.

The value of immunological approaches to the diagnosis of schistosomal myelopathy.

Myelopathy due to schistosome infection is a rare, yet probably frequently unrecognized, form of schistosomiasis. This condition is clinically difficult to diagnose, and without specific biopsy evidence final confirmation relies largely on circumstantial evidence. We describe here immunological attempts to diagnose schistosomal myelopathy. ELISA performed on the cerebrospinal fluid (CSF) was the most successful, detecting 12/12 cases tested prior to or within one month of treatment. This is based on a "normal" value established on neurological patients without myelopathy. Only 13/149 non-schistosomal myelopathy patients from an endemic area gave positive results in this test. Oligoclonal bands were detected in the CSF of 5/9 schistosomal myelopathy patients and 11/18 cases of myelopathy of other known causes, but in 0/7 cases of myelopathy where the cause was not established. Western blotting was unable to distinguish between myelopathy due to schistosomiasis and other causes. It is recommended that the ELISA be performed on CSF and the results be compared with a "normal" level for neurological patients. In our laboratory this system gives a high sensitivity and a negative result can be confidently used to exclude schistosomal myelopathy.

Diagnosis of neurocysticercosis by enzyme-linked immunosorbent assay.

The detection of neurocysticercosis by enzyme-linked immunosorbent assay, the criterion used for determining seropositivity and the method of interpreting results are discussed. Serum and cerebrospinal fluid (CSF) samples from each of 212 patients were analysed. The results showed that in some patients positive antibody titres may be found in only one specimen. If both specimens are analysed 87% of neurocysticercosis patients can be detected serologically. However, if only CSF is tested, the detection rate falls to 67%. It is recommended that clinicians submit both serum and CSF samples for analysis.

The value of an antigenic fraction of Cysticercus cellulosae in the serodiagnosis of cysticercosis.

Fractions of Taenia solium cysticerci were isolated using preparative isoelectric focusing. A fraction isoelectric between pH 7.8 and 10.0 was found to be most effective as an antigen in an enzyme-linked immunosorbent assay (ELISA) for anti-cyst antibodies. The efficacy of this fraction and of a total homogenate of the cysticerci to detect cases of neurocysticercosis by ELISA was compared. The partially purified fraction showed a sensitivity of 80% and specificity of 99.5%. The total homogenate had a sensitivity of 75% and a specificity of 99%. Cross-reactions occurred with sera from patients with hydatid disease. In patients with other parasitic infections the specificity of the isolated fraction (3/120) was considerably better than that of the total homogenate (16/120). Cysticercosis in man is caused by infection with the larval stage of the zoonotic pork tapeworm Taenia solium. The disease is largely one of developing countries and is prevalent in Latin America, Eastern Europe, the Far East and large parts of Africa. In the Republic of South Africa the prevalence of cysticercosis has been estimated as 8.5% amongst rural blacks, and in certain high incidence areas over 20%.

Serological detection of cysticercosis in two rural areas of South Africa.

Serological tests (ELISA) for cysticercosis were performed on groups of schoolchildren from two rural areas of Southern Africa, Ingwavuma in Northern KwaZulu and Isilimela in the Transkei. 22 of 736 Transkeian children were serologically positive while only 8 of 677 KwaZulu children were positive. These results, when corrected for the sensitivity and specificity of the test, indicate a cysticercosis prevalence of 2.49% in the Transkeian group and 0.23% in the KwaZulu group.

Serological techniques for the diagnosis of cysticercosis.

Three techniques--an indirect haemagglutination test, a fluorescent antibody test and enzyme-linked immunosorbent assay (ELISA)--have been established for the detection of cysticercosis antibodies in the serum or cerebrospinal fluid of patients with cysticercosis. Results obtained using these techniques have been compared to determine the most successful serodiagnostic method. In each test there was a marked difference between the detection of active and of calcified cysts. The results obtained using the three tests were remarkably similar, and none had a statistically significant advantage over the others with regard to the detection of cysticercosis antibodies. However, ELISA appears to have certain other advantages.

The influence of age, sex and breed of cattle on their muscle characteristics.

In order to gain more knowledge of the systematic changes occurring in meat tenderness and colour of different breeds and sexes of growing cattle, a number of characteristics were studied in five different muscles of Afrikaner and Friesland bulls and steers between birth and 24 months of age. Muscle collagen content of bulls was higher at birth than at all other ages and solubility of collagen decreased markedly between birth and 16 months of age. Shear force increased between 8 and 16 months, partially coinciding with the decrease in collagen solubility. Collagen content of muscles was higher in bulls than in steers and solubility decreased markedly between 12 and 16 months, only in the case of bulls. Afrikaner muscles were more tender than those of Frieslands and had a higher content and solubility of collagen. Pigment content was higher in Afrikaner than in Friesland muscles and increased steadily with age in all animals. The results show that the biological differences found to influence muscle characteristics were particularly those of age and breed of animal.