Observations on the patterns of blood IgM levels in the populations of endemic and nonendemic sleeping sickness areas in Kenya

Bull. Org. mond. Sant} 1972, 47, 757-767 Bull. Wid Hith Org. Observations on the patterns of blood IgM levels in the populations of endemic and nonendemic sleeping sickness areas in Kenya G. BINZ1 & H. J. C. WATSON 2 Increased levels ofserum immunoglobulin M (IgM) may be related to a wide range of antigenic stimuli provided by a variety of infections to which people are repeatedly exposed. Most, if not all, of the natural antibodies against bacterial and cellular antigens have been found to belong to the IgM class. It is known that IgM levels in the blood increase in trypanosomiasis but it is not possible to demonstrate trypanosomes in all persons who show raised IgM levels in serological surveys in an endemic sleeping sickness area. Although survey data are limited, this paper discusses the usefulness of IgM tests as an aid to the detection of Trypanosoma rhodesiense infections. The detection of abnormal levels of immuno- globulin M (IgM) in blood can be a useful indicator in the parasitological diagnosis of sleeping sickness, particularly if the infection is due to Trypanosoma gambiense or to the more chronic strains of T. rho- desiense. However, abnormal IgM levels can also be found in persons not suffering from trypanoso- miasis. In such cases, increased IgM production may be stimulated by subinfective doses of T. rhode- siense or T. gambiense, by nonpathogenic trypano- somes, or by pathogens other than trypanosomes. This article describes studies made in Kenya on IgM levels in persons not suffering from sleeping sickness. The studies were carried out during sur- veys undertaken mainly to detect cases of sleeping sickness, and the opportunity was taken to study IgM levels in human populations exposed to different tsetse and trypanosomiasis challenges, and to evalu- ate the possible effects of a limited number of other diseases on IgM levels. STUDY AREAS The main investigations reported in this commu- nication were conducted in the Lambwe Valley area, South Nyanza District, Kenya. A general description of this area (including a map showing 1 Project Technical Officer (Immunology), Present address: 1711 Ependes-Fribourg, Switzerland. " Project Medical Officer (Epidemiology). Present address: WHO, P.O. Box 9292, Dar es Salaam, Tanzania. the locations of survey areas) is given by Allsopp & Baldry (1972), while IgM levels in confirmed cases of sleeping sickness caused by T. rhodesiense and diagnosed in the area between 1968 and 1970 by Watson (1972) are described by Binz (1972). Com- parative IgM surveys were conducted partly in the Lambwe Valley (the Otuok and Obaluanda survey areas) and partly in three other localities in Kenya. Some relevant background information on these three latter areas is given below. During the Central Nyanza District survey, exami- nations were conducted only in the Yimbo and Sakwa localities, which border the eastern shore of Lake Victoria. This area has a history of T. gambiense and T. rhodesiense infections transmitted by the tse- tse flies Glossina fuscipes and G. pallidipes, respec- tively (see Baldry, 1972). Between 1965 and 1969, tsetse flies were largely eradicated from the area by ground spraying techniques ordered by the Govern- ment of Kenya. During the Nandi District survey, examinations were conducted at Kapsabet town, Rift Valley Province. The area was totally free of tsetse and had no history of tsetse infestation. During the Machakos District survey in Southern Province examinations were conducted at Kiboko, Makindu, and Kibwezi. This area had large game and livestock populations, and was heavily infected with G. pallidipes and G. longipennis; limited popula- tions of G. brevipalpis were also present. Although the area had a history of animal trypanosomiasis, 2961 - 757 G. BINZ & H. J. C. WATSON no cases of human sleeping sickness had been recorded there. MATERIALS AND METHODS Initial surveys for sleeping sickness were con- ducted in the endemic sleeping sickness area of the Lambwe Valley between June 1968 and August 1970 in eight contiguous survey areas (see Watson, 1972). Field investigations consisted of a brief clinical inspection of each person, the microscopic exami- nation of stained thick blood films, and the micro- scopic examination of gland fluid of persons with adenopathy. Blood samples were also taken on Whatman No. 4 filter paper for the subsequent determination of IgM levels. The whole available population of an area was examined whenever pos- sible, but public cooperation varied from place to place, and homesteads were sometimes found to be almost deserted at the time of the visit by the survey team. Subsequently, a more intensive search for trypano- somes was undertaken in a follow-up examination of those subjects who had a raised level of IgM at the time of the initial survey; this investigation involved direct microscopy and the inoculation of blood and cerebrospinal fluid into animals. In addi- tion, a clinical examination was made and some laboratory tests, e.g., the estimation of the erythro- cyte sedimentation rate and haemoglobin and exami- nations of stool and urine samples, were carried out routinely but under the prevailing field condi- tions all the tests were of necessity simple. Although 5 850 persons were examined during the initial surveys, only 5 814 dried blood samples were available for immunological examination. In all cases, blood IgM levels were determined by the single-diffusion technique of Cunningham et al. (1967), as described elsewhere by Binz (1972). IgM PATTERNS IN THE LAMBWE VALLEY AND CENTRAL NYANZA ENDEMIC SLEEPING SICKNESS AREAS Results of initial surveys Only two cases of sleeping sickness were diag- nosed during the initial surveys of the Lambwe Valley; both had raised levels of blood IgM. Of 148 old cases of sleeping sickness examined, 21 (14.2%) had raised IgM levels. Of the remaining 5 664 per- sons with no history of sleeping sickness, 286 (5.0 %) had raised IgM levels. The percentages of raised IgM in the Lambwe population were therefore as follows: (1) resulting from sleeping sickness, 0.7%; (2) possibly related to previous sleeping sickness, 6.8%; (3) attributable to other factors, 92.5%. The description that follows is based on a study of 307 subjects with raised IgM in a population of 5 812 from whom dried blood samples were obtained and examined; the 2 cases of sleeping sickness discovered during the surveys were excluded, the raised IgM level being attributed to the disease. The 148 old cases have been retained in the analysis for two reasons. First, there was no evidence that any of the old cases had not recovered (in fact, the group consisted of survivors from persons infected since 1955). In a person who had long been cured of the disease, it was unlikely that the raised IgM level could be attributed to the disease; the cause should be sought elsewhere. Second, there was little difference in the frequency of raised IgM according to age and sex among adults who had previously had sleeping sickness (21/142, or 14.7%) and those who had not (274/2 482, or 11.3%). The age and sex distribution of raised IgM levels in persons in the Lambwe Valley not suffering from sleeping sickness are presented in Table 1 for the area as a whole, and in Table 2 according to defined survey areas. It is evident from the results that the prevalence of raised levels of IgM increased with age. It re- mained at less than 0.5% in children up to the age of 10 years, gradually increased through puberty, increased more sharply through adolescence, and then remained at a steady level to middle age. The pattern was similar in both sexes. However, in women the abnormality was more common and there was a decline in old age; this was not apparent in men (Fig. 1). Although there were differences in the frequency of raised IgM levels in men and women in the eight survey areas (Table 2) they were not significant. Similarly, there appear to be no significant differences in the frequency of raised IgM in comparable age and sex groups from different areas. The determin- ing factor was age; otherwise, the abnormality appears to have been spread evenly in the popula- tion of the whole valley. Results of case area surveys in the Lambwe Valley Case area surveys were local surveys made with a view to finding additional cases in the environs of homesteads in which new cases of sleeping sick- ness had been diagnosed. They also gave the investi- gators an opportunity to study the epidemiological 758 BLOOD IgM LEVELS IN ENDEMIC AND NONENDEMIC SLEEPING SICKNESS AREAS Table 1. Age and sex distribution the Lambwe Valley of raised IgM levels in persons not suffering from sleeping sickness in Age groups (years) Sex 0-2 3-5 6-9 10-14 15-20 21-40 41.60 61 Total Males no. of persons examined 397 424 421 363 186 354 358 118 2621 raised IgM level (no.) 1 1 1 3 6 25 61 24 122 raised IgM level (%) 0.25 0.24 0.24 0.8 3.7 7.1 17.3 20.4 4.7 Females no. of persons examined 369 437 407 374 336 810 309 103 3 145 raised IgM level (no.) 1 0 1 4 11 79 68 21 185 raised IgM level (%) 0.3 0 0.25 1.1 3.3 9.7 22.0 21.0 5.9 Total no. of persons examined 766 861 828 737 522 1 164 667 221 5766 raised IgM level (no.) 2 1 2 7 17 104 129 45 307 raised IgM level (%) 0.26 0.12 0.24 0.95 3.4 8.9 19.5 20.0 5.3 aspects of the new cases and to assess the degree of risk to which other members of the homestead or settlement area were exposed. During these surveys 1 833 people were examined and 115 (6.3%) were found to have raised levels of IgM. Only 1 new case of sleeping sickness was found and the patient had a normal IgM level. Of 30 persons who had previously suffered from the disease, 3 (10.0%) had raised IgM levels. Among the remaining 1 802 persons with no history of infection, 112 (6.2%) had raised IgM levels. The proportions of raised IgM levels in the samples were therefore as follows: (1) resulting from sleeping sickness, 0.0%; (2) possibly related to previous sleeping sickness, 2.6%; (3) attributable to other factors, 97.4%. Results of the resurvey of the Otuok survey area, Lambwe Valley During the initial survey of the Otuok area, 7.4% of the adult population had raised IgM levels (Table 2). After the initial survey there was an influx of settlers, mainly Maragoli tribesmen and their livestock from northern Tanzania. Following the diagnosis of two cases of sleeping sickness in this new farming community, a number of other investigations were conducted and the presence of T. rhodesiense was revealed in cattle (Robson & Ashkar, 1972), in a reedbuck (Allsopp, 1972), and in the G. pallidipes population (England & Baldry, 1972). Entomological studies showed that a sizeable population of G. pallidipes was present in the area, and it could be assumed that many of the settlers and their livestock were receiving a continuous, and probably increasing, trypanosome challenge as more and more people developed the land adjacent to the main G. pallidipes habitat (Baldry, personal W 20 al _El 10 01 155 0 X Fig. 1. Frequency of raised IgM levels in persons from the Lambwe Valley, Kenya, according to sex and age. 759 760 G. BINZ & H. J. C. WATSON Table 2. Age and sex distribution of raised IgM levels in persons not suffering from sleeping sickness in defined survey areas in the Lambwe Valley Adults @ Children All persons M F Total M F Total M F Total Obaluanda no. examined 197 317 514 286 268 554 483 585 1 068 raised level (no.) 25 54 79 3 2 5 28 56 84 raised level (%) 12.7 17.0 15.4 1.0 0.7 0.9 5.8 9.6 7.9 Kaksingiri no. examined 188 370 558 357 328 685 545 698 1 243 raised level (no.) 26 38 64 2 0 2 28 38 66 raised level (%) 13.2 10.0 11.2 0.6 0 0.3 5.0 5.4 5.2 West Ruma no. examined 148 193 341 204 227 431 352 420 772 raised level (no.) 13 20 33 1 2 3 14 22 36 raised level (%) 8.8 10.3 9.7 0.5 0.9 0.7 3.8 5.2 4.7 Otuok no. examined 57 78 135 80 81 161 137 159 296 raised level (no.) 7 3 10 0 0 0 7 3 10 raised level (%) 12.5 3.8 7.4 0 0 0 5.1 1.8 3.3 Wiga no. examined 186 272 458 274 276 550 460 548 1 008 raised level (no.) 20 37 57 0 1 1 20 38 58 raised level (%) 10.8 13.6 12.4 0 0.4 0.2 4.3 6.9 5.8 Magunga no. examined 192 286 478 369 368 737 561 654 1 215 raised level (no.) 17 17 34 0 0 0 17 17 34 raised level (%) 8.8 5.9 7.1 0 0 0 3.0 2.5 2.7 Masangala no. examined 23 33 56 52 34 86 75 67 142 raised level (no.) 6 4 10 0 0 0 6 4 10 raised level (%) 26.1 12.1 17.8 0 0 0 8.0 6.0 7.0 Escarpment no. examined 13 17 30 18 20 38 31 37 68 raised level (no.) 4 5 9 0 0 0 4 5 9 raised level (%) 30.4 29.4 30.0 0 0 0 12.9 13.5 13.2 Total no. examined 1 004 1 566 2 570 1 640 1 602 3 242 2 644 3168 5 812 raised level (no.) 118 178 296 6 5 11 124 183 307 raised level (%) 11.6 11.4 11.5 0.4 0.3 0.34 4.7 5.8 5.3 a Aged 15 years or more. BLOOD IgM LEVELS IN ENDEMIC AND NONENDEMIC SLEEPING SICKNESS AREAS communication). In view of this situation, the area was resurveyed 5 months after the initial survey to determine the frequency of raised IgM levels. Of the 90 adults examined, 18 (20.0%) had raised IgM levels, clearly showing that during the 5-month period between the two surveys there had been a very appreciable increase in the frequency of raised IgM, i.e., from 7.4% to 20.0%. Results of the resurvey of the Obaluanda survey area, Lambwe Valley During the initial survey of the Obaluanda area, 15.4% of the adult population had raised IgM levels (Table 2). Subsequently, G. pallidipes was eradicated from the area by ground spraying teams commis- sioned by the Government of Kenya. However, to the south of the area certain thickets, particularly the large Ruma thicket, remained infested with tsetse. Entomological surveys of the north-eastern sector indicated that G. pallidipes had in fact been eradicated and it was therefore decided to carry out an immunological resurvey in this sector to deter- mine the influence of the tsetse-eradication campaign on IgM levels in the human population. Of 268 adults examined, 19 (7.0%) had raised IgM levels, show- ing that in less than 2 years after the eradication of tsetse there had been an appreciable reduction in the frequency of raised IgM, i.e., from 15.4% to 7.0%. Results of a post-tsetse-eradication survey in Central Nyanza District Following a tsetse-eradication campaign organized by the Government of Kenya in 1965-69 in the Yimbo and Sakwa locations of Central Nyanza District, two cases of sleeping sickness were diag- nosed, both of them in children. An immunological survey was therefore conducted in these two loca- lities and 599 adults and 638 children were examined. The results of the survey are summarized in the following tabulation. persons examined new cases of sleeping sickness old cases of sleeping sickness persons with no history of sleeping sickness a Two of these persons w No. of Number persons with raised IgM levels Frequency of raised IgM (%J 1237 31 a 2.5 From these findings it is deduced that 1.8% of raised IgM levels could be attributed to previous sleeping sickness and 98.2% to other factors. IgM PATTERNS IN THE MACHAKOS AND NANDI DISTRICT NONENDEMIC AREAS In endemic sleeping sickness areas, raised IgM levels in some people who are not suffering from sleeping sickness could be caused by either non- infective doses of T. rhodesiense or doses of non- pathogenic trypanosomes, i.e., T. brucei, T. con- golense, and T. vivax. Two surveys were therefore initiated with a view to assessing the possible effects of animal trypanosomes on IgM levels in man. One survey was made in an area having tsetse and animal trypanosomiasis but no sleeping sickness (Machakos) and the other survey in an area having no tsetse, animal trypanosomiasis, or sleeping sick- ness (Nandi). Results of the Machakos District survey This survey covered three small areas-namely, Kiboko, Makindu, and Kibwezi. The number of adult persons examined and the frequency of raised IgM in the three areas is shown in the following tabulation. No. of No. ofpersons with Area persons raised IgM examined mak female total Kiboko Makindu Kibwezi totals 233 413 384 1 030 8 3 15 26 2 3 8 13 10 6 23 39 Frequency of raised JgM (%) 4.5 1.5 6.0 3.8 The age and sex distribution of raised IgM levels in the subjects examined is shown in Table 3. Evidently, some factors that provoke a raised IgM level existed in the area, although the three sub-areas were not equally affected. Since there was no opportunity to study tsetse and trypanosome populations in the three sub-areas, no explanation can be offered for the variations. Results of the Nandi District survey 0 0 0.0 This survey was conducted at Kapsabet town, 23 4 17.4 in an area completely free from tsetse and tsetse- borne trypanosomiasis. Of 878 adults examined, 1 214 27 2.2 only 1 subject (0.1 %) in the 41-60-years age group ere children. had a raised level of IgM, indicating that the factors 6 761 G. BINZ & H. J. C. WATSON Table 3. Age and sex distribution of raised IgM levels in adults in the Machakos District nonendemic sleeping sickness area Age group Sex 15-20 21-40 41-60 > 61 Total Males no. of persons examined 59 254 122 42 477 raised IgM level (no.) 0 11 7 8 26 raised IgM level (%) 0 4.3 5.7 19.0 5.4 Females no. of persons examined 94 280 127 42 543 raised IgM level (no.) 1 9 1 2 13 raised IgM level (%) 1.0 3.2 0.7 4.7 2.3 Total no. of persons examined 153 534 249 84 1 020 raised IgM level (no.) 1 20 8 10 39 raised IgM level (%) 0.6 3.7 3.2 12.0 3.8 that provoke raised IgM levels were virtually absent from the area. T1HE POSSIBLE RELATIONSHIP BETWEEN RAISED IgM LEVELS AND SPECIFIC INFECTIONS The factors that may be involved in elevated IgM levels can be studied by considering either the presence or absence of a specific infection in the individual or environmental factors. At present, the effect of environmental factors (e.g., proximity to game animals, herds of cattle, and other, possibly relevant, ecological associations), on the health and wellbeing of the individual or community in relation to trypanosomiasis can be less well measured. A number of diseases, particularly leprosy and leu- kaemia, are known to be associated with a raised level of blood IgM. The latter disease is extremely rare in surveyed areas ofKenya and ofno importance in an examination of the factors associated with a 5% frequency of raised IgM in the community. It must be borne in mind that the purpose of the surveys in the Lambwe Valley was to find cases of sleeping,sickness, the IgM test being used as a screening method. The purpose was not to investi- gate other causes of raised IgM levels in the popula- tion and consequently, the data available for a study of the problem are limited. At the time of the initial Lambwe surveys, blood films were made from all subjects; thus information was available on trypano- some and malaria infections in all persons whose IgM levels were investigated. However, records were not made of the occurrence of other diseases. At follow-up examinations, when clinical and labora- tory investigations were made, the presence or absence of leprosy, urinary schistosomiasis, and intestinal helminths and the results of some simple laboratory tests were recorded for each person. This information was available for subjects who had raised levels of IgM and who were followed up, and also for a smaller group of control subjects with normal IgM levels. In analysing the association between raised levels of IgM and malaria infection, the results from one of the eight survey areas (Kaksingiri) have been omitted because the examination of stained blood films for malaria parasites was not considered to be entirely satisfactory at the time that area was sur- veyed. The results of the analysis are presented in Table 4 and show that there was no positive relation- ship between raised IgM levels and malaria infection. Malaria is holoendemic in the Lambwe Valley, parasites being found at the examination of a single blood film in 44.6% of the 4 564 persons investigated at the time of the initial surveys. It can be argued that the examination of only one blood film from each subject gives no accurate indication of his 762 BLOOD IgM LEVELS IN ENDEMIC AND NONENDEMIC SLEEPING SICKNESS AREAS Table 4. Results of examinations of blood films for malaria parasites compared with IgM levels in persons with no history of sleeping sickness in the Lambwe Valley No. (and percentage) of persons with the Result of following conditions examination Raised IgM Normal IgM Ttl level level Totals parasites seen 44 (2.2) 1 991 (97.8) 2035 parasite not seen 184 (7.3) 2 345 (92.7) 2 529 totals 228 (5.0) 4 336 (95.0) 4 564 long-term status in relation to the disease and that it must be assumed that everyone is infected in childhood, the survivors having developed a degree of immunity. Nevertheless, it appeared that there was no association between raised IgM levels and malaria infection; if there had been some asso- ciation, the IgM level would have been highest at the time of the maximum infection in the early years of life. This is contrary to our findings. Moreover, although nearly 45% of the population had a parasitaemia at the time of the survey, the frequency of raised IgM was only 5.0% and, as can be seen from Table 4, of the 228 subjects with raised IgM levels only 44 (19.3%) had an apparent malaria parasitaemia. In the group with normal IgM levels, 46.0% had an apparent malaria para- sitaemia. It is also equally clear that IgM levels were not associated with the development of immu- nity to malaria, since immunity begins to appear well below the age of 10 years; this is not reflected in the results shown in Fig. 1. Since the only infections recorded in the initial survey were trypanosomiasis and malaria, IgM levels can be properly examined only in association with these two diseases. During subsequent follow-up studies, clinical examinations revealed cases of lep- rosy, while laboratory investigations revealed urinary and intestinal helminth infections. However, the sub- jects seen were only those with raised IgM levels and a number of control subjects (persons with nor- mal IgM levels at the time of the initial survey who were investigated in the same way). The number of controls was quite small because it was felt to be unjustified to subject these persons to the full follow-up procedures and, in particular, lumbar puncture. Although leprosy was endemic in South Nyanza, only three cases were diagnosed during the study period, as shown in the following tabulation. No. of No. of persons with persons with raised IgM normal IgM levels levels no. of persons seen at follow-up no. of leprosy cases no. of persons without leprosy 285 125 3 0 282 125 No conclusions can be drawn from these small numbers, but it is interesting to note that raised IgM levels were found in all three cases of leprosy. Although schistosomiasis was endemic in the Lambwe area, transmission probably occurred only along the shores of Lake Victoria and the lower Olambwe River. Data on the incidence of schisto- somiasis and IgM levels given in Table 5 indicate that schistosome infections do not always cause abnormal IgM levels. It is also evident from the Table 5. Results of examinations for schistosome infections compared with IgM levels in persons with no history of sleeping sickness in the Lambwe Valley. No. (and percentage) of persons with the following conditions: Result of examination Raised IgM Normal IgM Totals level level Schistosoma mansonifound 7 (2.9) 7 (6.5) 14 (4.0) S. haematobium found 4 (1.7) 0 (0.0) 4 (1.2) total schistosomiasis found 11 (4.6) 7 (6.5) 18 (5.2) no. of schistomosomes found 217 (70.0) 93 (30.0) 310 (89.6) 763 0. BINZ & H. J. C. WATSON Table 6. Results of stool examinations for helminth infections, compared with IgM levels in persons with no history of sleeping sickness in the Lambwe Valley No. (and percentage) of persons with the following Results of examination conditions Raised 1gM Normal IgM Totalslevel level no. of specimens examined 239 (69.1) 107 (30.9) 346 (100) Ancylostoma present 17 (7.1) 2 (1.9) 19 (5.5) Ascaris present 40 (16.7) 22 (20.5) 62 (17.9) Taenia present 7 (2.9) 11 (10.3) 18 (5.2) no. of helminths found 175 (73.2) 72 (67.3) 247 (71.4) results of stool examinations (Table 6) that helminth infections do not invariably lead to abnormally high IgM levels; in fact, there was nothing to suggest that there was any form of association between the two factors. ASSOCIATIONS BETWEEN ABNORMAL IgM LEVELS AND OTHER CLINICOPATHOLOGICAL FINDINGS The erythrocyte sedimentation rates were mea- sured, a reading above 30 mm per hour by the Westergren method being considered as abnormal, and haemoglobin estimations were made. Subjects with less than 60% haemoglobin on the Haldane standard were considered to be abnormal. At the same time, the abdomen of each person was palpated to detect any enlargement of the liver or spleen. The results are summarized in the following tabu- lation. Erythrocyte sedimentation rate no. examined no. abnormal percentage abnormal Haemoglobin level no. examined no. abnormal percentage abnormal Splenomegaly no. examined no. enlarged percentage enlarged No. of persons with raised IgM levels 270 233 86.2 264 51 19.3 285 104 36.5 Hepatomegaly no. examined no. enlarged percentage enlarged 285 47 16.5 125 22 17.6 From the data presented above there appears to be no association between raised IgM levels and hepatomegaly. In the other three cases, abnormal findings appear to have been found most commonly in persons with raised IgM levels, suggesting that various underlying pathological conditions that cause an increase in IgM may also contribute to some degree of anaemia, raised erythrocyte sedimentation rates, and spleen enlargement. ASSOCIATIONS BETWEEN ABNORMAL lgM LEVELS AND NONPERSONAL (ENVIRONMENTAL) FACTORS At the time when sleeping sickness surveys were No. of conducted in the Lambwe Valley, investigations were persons with also made on trypanosomiasis in domestic stocknormal 1gMlevels (Robson & Ashkar, 1972) and on G. pallidipes (England & Baldry, 1972). A number of possible associations with the pattern of raised IgM levels 121 can therefore be examined. 60 With regard to the influence of cattle on the 49.5 incidence of raised IgM levels in man, there appeared to be no significant difference between people whose cattle were infected and those whose cattle were not113 infected. There was also no significant difference8 between the populations of households in which7.0 there were noninfected cattle and those in which there were no cattle. However, there was a possibly 125 significant difference between households in which 22 there were infected cattle and those with no cattle, 17.6 as shown in the following tabulation. 764 BLOOD IgM LEVELS IN ENDEMIC ANI) NONENDEMIC SLEEPING SICKNESS AREAS adults raised IgM levels raised IgM levels (%) The presence steads and the pi levels in the hom homesteads were dipes habitats. Hi bly of little imp( of people movin! were more likel3 lenges away froi their homestead- steads were loca pallidipes. During the fie 309 persons wer IgM levels, but c sickness. In a fu abnormality coul No. of No. of No. of somal infection, particularly as Binz (1972) hashouseholds households households Number with with with shown that blood IgM levels may remain high for infected noninfected no cattle cattle cattle as long as 2 years after the successful treatment of 2 598 748 280 1 570 sleeping sickness. In the remaining 286 persons (92.5 %) with raised IgM levels no definite diagnosis could be made. 309 106 28 175 However, it appears from the findings as a whole that in areas such as the Lambwe Valley, where 11.9 14.2 10.0 11.1 there are tsetse and confirmed cases of human and animal trypanosomiasis, or in localities, such as of G. pallidipes in or near home- exist in the Machakos District, where there are resence of persons with raised IgM tsetse and animal trypanosomiasis, people are more estead was slightly significant if the likely to exhibit abnormal IgM levels than those located 1 km or less from G. palli- living in areas such as the Nandi District that are Dwever, this association was proba- free from both tsetse and trypanosomiasis (Table 7).)rtance because, with the majority The sex of the subject appears to have little or no g about the area on foot, persons effect on the frequency of raised IgM levels but to encounter trypanosome chal- there seems to be a correlation with age. There was mn the immediate surroundings of an increase in the frequency of raised IgM levels in -unless, of course, their home- both sexes from the 15th year onwards. In women ted inside thickets infested by G. over the age of 60 years there was a slight fall in IgM levels, but the increase continued in men. There was no correlation between abnormal IgM DISCUSSION levels and any of the specific diseases that the authors were able to study (malaria, schistosomiasis, leprosy, Id surveys in the Lambwe Valley, and helminthiases). Even malaria, which one might e found to have abnormal blood have been expected to provide an IgM response, only 2 of these (0.7%) had sleeping appeared not to be associated with the findings irther 21 persons (6.8%) the IgM reported; only 2.2% of malaria cases had a raised d be attributed to previous trypano- IgM level. Table 7. Frequency of raised IgM levels in adult human subjects exposed to different types of tsetse-trypanoso- miasis situations in Kenya Features of the locality Percentage Locality prevalence Tsetse Sleeping Animal of raised IgMsickness trypanosomes levels in man Lambwe Valley (overall endemic area) present present present 11.5 Otuok (Lambwe): increasing tsetse challenge to an expanding human and livestock population (1) soon after immigrants arrived present present present 7.4 (2) 6 months later present present present 20.0 Central Nyanza after tsetse control presumed absent presumed absent present a 4.8 Obaluanda (Lambwe): declining tsetse challenge (1) before tsetse control present present present 15.8 (2) after tsetse control presumed absent presumed absent present 7.0 Machakos District present absent present 3.8 Nandi District absent absent presumed absent 0.1 ' In the absence of tsetse, some types of animal trypanosomiasis can be transmitted by other biting flies. 765 G. BINZ & H. J. C. WATSON Of 270 people with raised levels of IgM, 233 (86.2 %) also had an abnormal erythrocyte sedimen- tation rate, suggesting that increased concentrations of serum IgM may cause clumping of erythrocytes and thus hasten their sedimentation rate. Support for this hypothesis is probably provided by the fact that rouleau formations and cold erythrocyte agglu- tinins were frequently noted in peripheral blood smears. In a control group of subjects with normal Igm levels, 49.5% had an abnormal erythrocyte sedimentation rate. Haemoglobin levels were abnormal in 19.3 % of a sample of 264 persons with raised IgM levels. In a control group of 113 subjects with normal IgM levels, the haemoglobin levels were abnormal in only 7.0% of the sample, suggesting that there may also be a positive correlation between IgM and haemoglobin levels. Splenomegaly was present in 36.5% of 285 persons examined who had raised IgM levels. In the control group of 125 subjects with normal IgM levels, only 17.6% had an enlarged spleen. Both anaemia and splenomegaly could be asso- ciated with the macroglobulinaemia of the raised level of IgM. No haematological examinations were made except those incidental to the search for try- panosomes and malaria parasites. A high level of IgM could have been associated with Waldenstr6m's disease, but the frequency was too high for this disease to account for all the cases of raised IgM level. Clinical examination of these persons gave no evidence of epistaxis, gingivitis haemorragica, or neurological disturbances. It is known that the production of IgM is an early immunological response to bacterial or cellular antigens. The repeated stimulus of a large antigen (perhaps a trypanosome) may cause the production of IgM to reach a high and constant level; such high production rates were observed where the trypano- some challenge was greatest (Table 7). ACKNOWLEDGEMENTS The authors are grateful to the Director of Veterinary Services and to the Chief Zoologist, Ministry of Agriculture, Kenya, for the provision of facilities at the Lambwe Valley Field Station. RItSUMI OBSERVATIONS SUR LES ASPECTS DES CONCENTRATIONS SANGUINES D'IgM DANS LES POPULATIONS DE REGIONS D'ENDEMICITE OU DE NON-ENDtMICITl TRYPANOSOMIENNE AU KENYA Des enquetes intensives ont e't menees de 1968 A 1971 dans la vall6e de la Lambwe, ou la trypanosomiase A Trypanosoma rhodesiense est end6mique, afin d'etudier les concentrations sanguines d'immunoglobuline M (1gM) chez les habitants de la region. Ces recherches ont com- porte dans chaque cas un examen clinique sommaire, l'examen microscopique de gouttes 6paisses et, en cas d'addnopathie, du suc ganglionnaire. Des echantillons de sang ont et6 recueillis sur papier filtre pour titrage de l'IgM. Ces premieres enquetes ont ete suivies d'une autre au cours de laquelle les sujets presentant une augmen- tation des titres seriques d'fgM ont fait l'objet d'investi- gations plus pouss6es: examen microscopique direct et inoculation A I'animal du sang et du liquide cephalo- rachidien, mesure de la vitesse de sedimentation des hematies et du taux d'hemoglobine, examen de selles et d'urine. Etudiant les facteurs qui peuvent etre a l'origine d'une augmentation de la teneur du sang en IgM, les auteurs examinent les rapports entre cette anomalie et la trypano- somiase, le paludisme, la lepre, la schistosomiase et les helminthiases intestinales. Les associations eventuelles entre l'augmentation des titres d'IgM et d'autres troubles decel6s par les examens cliniques (hepatomegalie, spl6no- megalie, an6mie, augmentation de la vitesse de sedimen- tation des h6maties) sont egalement discutees, ainsi que le r6le possible des facteurs de milieu. Cette analyse ne fait ressortir aucune correlation nette entre les concentrations anormales d'IgM et une maladie specifique, un trouble pathologique ou un facteur de milieu. On pense cependant que la prevalence des concen- trations 6lev6es d'IgM pourrait refleter l'intensite de la stimulation antigenique par T. rhodesiense ou peut-etre par des trypanosomes d'animaux non pathogenes pour l'homme. Il semble que l'emploi simultane des techniques parasitologiques et immunologiques (titrage de l'IgM) se prete mieux A l'evaluation de la circulation des trypano- somes dans une collectivite qu'au diagnostic des infections individuelles. 766 BLOOD IgM LEVELS IN ENDEMIC AND NONENDEMIC SLEEPING SICKNESS AREAS 767 REFERENCES Allsopp, R. (1972) Bull. Wid Hlth Org., 47, 735 Allsopp, R. & Baldry, D. A. T. (1972) Bull. Wld Hlth Org., 47, 691 Baldry, D. A. T. (1972) Bull. Wld Hlth Org., 47, 699 Binz, G. (1972) Bull. Wid Hlth Org., 47, 751 Cunningham, M. P. et al. (1967) Trans. roy. Soc. trop. Med. Hyg., 61, 688 England, E. C. & Baldry, D. A. T. (1972) Bull. Wld Hlth Org., 47, 785 Robson, J. & Ashkar, T. S. (1972) Bull. Wid Hlth Org., 47, 727 Watson, H. J. C. (1972) Bull. Wid Hlth Org., 47, 719