The identification of Trypanosoma brucei gambiense in Liberian pigs and dogs by isoenzymes and by resistance to human plasma

29 Trypanozoon stocks from Liberian pigs and dogs were screened for human plasma resistance and electrophoretic isoenzyme patterns of eleven enzymes. Two stocks from pigs were found both to be resistant to human plasma and to have an isoenzyme marker, a slow alanine aminotransferase (ALAT) pattern, previously found only in Trypanosoma brucei gambiense from man. This constitutes evidence that the pig is a reservoir of human trypanosomiasis in West Africa. The T.b.gambiense ALAT was also found in stocks from 5 other pigs and a dog, but none of these stocks was resistant to human plasma; conversely, 9 further isolations from pigs and 2 from dogs were plasma resistant but did not have the T.b.gambiense ALAT. The lack of correspondence between the two characteristics is discussed. A T.b.gambiense stock from man in Zaire had the ALAT pattern characteristic of T.b.gambiense from Senegal and Nigeria, together with the ASAT triplet found in most T.b.gambiense stocks. Peptidase polymorphism was shown in trypanosomes for the first time.

The influence of lorry transport on the Trypanosoma vivax infection rate in Nigerian trade cattle

In Nigeria in 1974 and 1975 there was an apparent sharp reduction in the prevalence of trypanosomiasis of cattle at several markets and control points. Some of the decrease appears to be due to the tsetse eradication programmes and Sahelian drought, but the change to lory transport as the principal means of moving cattle from the northern grazing areas to the south-western markets, which replaced a trek of at least three weeks, was probably an important factor.

Identification of economically important parasites

The taxonomy of a parasite can be an important guide to its pathogenic characteristics. A wide range of anatomical, biochemical and behavioural tests is now being developed to define different strains and subspecies of the main tropical parasites.

Biochemical characterization of some species of Trypansoma (Schizotrypanum) from bats (Microchiroptera)

Trypanosoma (Schizotryanum) species isolated from bats (Microchirotera) in Europe and Latin America were examined by determining the buoyant densities of their nuclear and kinetoplastic deoxyribonucleic acid (DNA) and the electrophoretic patterns of six isoenzymes. By these criteria they were separated into three distinct groups -- two from Europe (T. dionisii and T. vespertilionis) and one from America. T. dionisii was also separable by its morphology in vitro. Geographical location and DNA buoyant densities suggested that the American stocks were more closely related to T. cruzi than to the European species, though they differed from it marginally in kinetoplastic DNA density and in being noninfective to mice. Similar stocks studied by other workers have been shown to differ from T. cruzi also in reduced infectivity to, and lack of natural association with, Triatominae, and in antigenic composition. It is therefore proposed that trypanosomes of the subgenus Schizotryanum occuring naturally in Microchiroptera and differing from T. cruzi sensu stricto as outlined above should be treated as a distinct subspecies, T. cruzi marinkellei ssp. nov. T. cruzi sensu stricto thus becomes the nominate subspecies T. cruzi cruze Chagas 1909.

The identification by isoenzyme patterns of two distinct strain-groups of Trypanosoma cruzi, circulating independently in a rural area of Brazil

Culture forms of 17 Trypanosoma cruzi stocks, primarily isolated from a rural area of endemic Chagas disease at São Felipe, Bahia, Brazil, were compared by the electrophoretic patterns of six enzymes: aspartate aminotransferase, alanine aminotransferase, glucose-6-phosphate dehydrogenase, malate dehydrogenase (decarb-oxylating) (NADP+), glucosephosphate isomerase and phosphoglucomutase. Two markedly distinct combinations of isoenzyme patterns were seen, justifying the arrangement of the 17 stocks into two strain-groups, each of which was enzymically homogeneous. One combination was characteristic of the 11 domestic stocks of T. cruzi derived from both human infections and domiciliated animals; the second was characteristic of the six sylvatic stocks derived from opossums and a sylvatic triatomine species. The enzyme patterns were independent of the original host and the type of culture medium used. Distinction of the two strain-groups accords with epidemiological evidence that the domestic and sylvatic transmission cycles in São Felipe do not overlap. It is suggested that the diverse enzyme characters of the two strain-groups circulating in São Felipe reflect diverse origins; the domestic form of T. cruzi probably invaded the area from the south of Brazil with the domestic triatomine vector, Panstrongylus megistus.

Enzyme electrophoresis in characterizing the causative organism of Gambian trypanosomiasis

Trypanosoma (Trypanozoon) brucei includes three morphologically identical subspecies which are poorly defined by clinical behaviour; T. b. brucei does not infect man, whereas T. b. rhodesiense causes an acute, and T. b gambiense a chronic, disease. Thirty-three isolates of the complex, each of which had previously been identified on clinical or other criteria, were compared by the electrophoretic patterns of two trypanosomal enzymes, alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT). One particular ALAT pattern clearly segregated a group of human pathogens of which all except one were labelled T. b. gambiense. The exception was labelled T. b. rhodesiense, and in addition three putative T. b. gambiense isolates did not have this pattern; it is suggested that only one presents a serious anomaly. The T. b. gambiense group could also be subdivided by three ASAT patterns which coincided with known groupings based on serological criteria.

Isoenzymes of two aminotransferases among Trypanosoma vivax in Nigerian cattle

During a period of three months, thin-layer starch-gel electrophoresis was used to examine the isoenzymes of alanine and asparate aminotransferases from samples of T. vivax collected from naturally infected Nigerian cattle. Experimentally infected cattle sheep and goats were also studied. Three patterns, termed Sets 1,2 and 3, differed in both enzymes. The stability of the enzyme patterns was generally confirmed in experimental animals. The results are discussed in relation to subspeciation in T. vivax.

Diagnosis of Gambian trypanosomiasis in man by isolating trypanosomes from blood passed through DEAE-cellulose

A method is described whereby small numbers of trypanosomes in blood can be concentrated free of blood cells on to a slide. Infected blood is passed through a column of DEAE-cellulose, which adsorbs the blood cells, and the organisms are separated from the eluate by centrifugation. By this technique trypanosomes were detected in 24% of 41 Nigerian patients with suspected Gambian trypanosomiasis, but whose cervical lymph glands were not infected; of these, only 5% were positive in thick blood films. Trypanosomes were also found in 91% of 21 gland-positive patients, of which only 19% were positive in thick blood-films. The organisms could not be found in 5 patients recently treated with either pentamidine or suramin-sodium and melarsen, and disappeared within two hours from the blood of another patient given melarsoprol. Trypanosomes were not found in 3 samples of infected cerebrospinal fluid passed through DEAE-cellulose. Although 2 gland-positive patients and 1 patient with a patent parasitaemia failed to give positive results, column-separation of suspected blood is a potentially valuable aid in the parasitological diagnosis of Gambian trypanosomiasis.