IgM deficiency in Nigerians

CORRESPONDENCE Evidence of possible molhwcicide resistance in Schistosoma intermediate hosts from Iran? Sra-Mollusciciding has now been applied for more than 10 years in many areas where schistosomiasis is endemic. Mollusciciding results in a heavy selection pressure in favour of molluscicide-resistant snails and the experiments described in this letter provide evidence that molluscicide resistance has developed in Bulinus truncatus. In Khuzestan, Iran, mollusciciding has taken place since 1966 once a year using Bayluscide in a concentration of 1.0 mg/l (MASSOUD,personal communication). Two laboratory stocks of B. truncatus have yielded material for this comparative investigation on molluscicide resistance. The stocks were established at the Danish Bilharziasis Laboratory in 1967 and 1977 respectively from material originating from Dezful, Iran and received from Dr. S. Massoud. The Bayluscide solution used in the experiments was prepared by adding 25 ~1Bayluscide 25 % Emulsifiable concentrate to 10 litres of pond water. Snails from the two stocks were exposed simultaneously to the Bayluscide, washed twice in pond water and then allowed to recover overnight in small vials containing one snail, before the numbers of live and dead snails were determined. Snails of 2-4 mg weight (shell height 2-3 mm) were exposed for 4 hours and 20 minutes. Of the 1967 snails, three out of 25 specimens survived compared to 23 survivors out of 28 snails from the 1977 stock. Snails of 9-10 mg (shell height 3-4 mm) were exposed for 5 hours. Of the 1967 snails 18 died and seven survived but all 24 snails from the 1977 stock survived. These results show that within both size groups of Bulinus truncafus the I977 stock displays a significantly higher resistance to Bayluscide than does the 1967 stock. I am, etc., J. E. JELNES Dansk Bilharziose Laboratorium, Jaegersborg All& I D, DK 2920 Charlottenlund, Denmark Accepted for publication 29th June, 1977.

Incubation and prepatent periods of Plasmodium vivax SIR-I wish to comment on the reports by SHUTEet al. (1976) and UNGUREANUet al. (1976) on the relationship of the number of sporozoites inoculated to the length of the incubation and prepatent periods in vivax malaria. These authors distinguish between short prepatent periods (SPP) and lona ureoatent oeriods (LPP). which thev believe to be produced by-two kinds of sporozoites, designated Type I and Type II, respectively. They base their conclusion on observations of the prepatent period in infections produced by graded doses of sporozoites of temperate (Korea) and tropical (New Guinea) strains of the parasite. SHOE et al. (1976) observed the LPP (257 to 628 days) in ten subjects inoculated with 10, 100 or 1,000 sporozoites of the Korean strain. They observed the SPP (13 to 16 days) in one subject inoculated with 1,000 sporozoites and in five subjects inoculated with 100,000 sporozoites. While it is true that no prepatent periods between 16 and 257 days were observed, it is also true that no infections initiated with the 10,000 sporozoite dosage were studied. From the data given it can be

451

calculated statistically that T=568-108 log N, where T is the prepatent period in days and N is the number of sporozoites inoculated. From this equation it can be estimated that the prepatent period of an infection initiated with 10,000 sporozoites would be 136 days. Thus, the missing dosage (10,000 sporozoites) corresponds exactly to the intermediate prepatent period that the authors did not obtain in their study: (16+257)/2 = 136.5 days. UNGUREANUet al. (1976) observed the SPP (12 to 17 days) in 11 subjects inoculated with 10, 100, 1,000 or 10,000 sporozoites of the New Guinea strain; the LPP was not observed. In this case, T = 18.3- 1.42 log N, and it is clear that the dose-response relationship was very different in the two strains. However, the semilogarithmic correlation of sporozoite doses and prepatent periods was highly significant in both studies (r=-0.85 for the Korean strain, -0.88 for the New Guinea strain), and it therefore seems unnecessary to construct a discontinuous model to explain the facts presented. SHUTE et al. (1976) explain the LPP in terms of a presumed seasonal advantage that would accrue to the temperate (Korean) strain. However, several of the LPP’s observed (329, 345, 355, 365, 386, 386, 387 days) were very nearly equal to the length of the year, and in such cases the LPP would not shift the season of patent parasitaemia as the authors suggest. While I do not dispute the seasonality of vivax malaria (RUTLEDGEet al., 1969), I do not feel that sporozoite differentiation is necessarily involved in its production or that the data presented support that interpretation. I am, etc., L. C. RUTLEDGE Department of Tropical Medicine, Letterman Army Institute of Research, Presidio of San Francisco, CA 94129, U.S.A. References Rutledge, L. C., Gould, D. J. & Tantichareon, B. (1969). Factors affecting the infection of anophelines with human malaria in Thailand. Transactions of the Royal Society of Tropical Medicine and Hygiene, 63,613-619. Shute, P. G., Lupascu, Gh., Branzel, P., Maryon, M., Constantinescu, P., Bruce-Chwatt, L. J., Draper, C. C., Killick-Kendrick, R. & Garnham, P. C. C. (1976). A strain of Plasmodium vivax characterized by prolonged incubation: the effect of numbers of sporozoites on the length of the prepatent period. Transactions of the Royal Society of Tropical Medicine and Hygiene, 70,474-481. Ungureanu, E., Killick-Kendrick, R., Garnham, P. C. C., Branzel, P., Romanescu, C. & Shute, P. G. (1976). Prepatent periods of a tropical strain of Plasmodium vivax after inoculations of tenfold dilutions of sporozoites. Transactions of the Royal Society of Tropical Medicine and Hygiene, 70, 482-483. Accepted for publication 10th July, 1977.

IgM deficiency in Nigerians Sir-Demonstration of a high serum IgM has proved to be a valuable way of diagnosing the tropical splenomegaly syndrome but little attention has been paid to the significance of a low serum IgM in a person living in an area of high malaria endemicity. SAGOE (1970) reported low serum IgM levels in Nigerian patients with

452

CORRESPONDENCE

chronic lymphatic leucaemia and CORNILLE-BROGGER (1975) recently described the occurrence of primary IgM deficiency in a healthy Nigerian. This report prompted us to review the results of IgM determinations carried out in our laboratory over the past four years. During the aeriod November 1973-June 1976. 1.026 sera were submitted to the Immunology laboratory’ for IgM determination; most of these samples came from patients with splenomegaly who were suspected of having the tropical splenomegaly syndrome. 43 patients had an IgM of < 104 IU/ml-a value of less than two standard deviations below the geometric mean value (338 III/ml) of 97 healthy adult Nigerians. The diagnoses made in these 43 patients are shown in the table. It is unlikely that any of the patients had primary IgM deficiency. Half the patients had a malignancy-usually chronic lymphatic leucaemia or a lymphoma-showing that in this Dart of Nigeria. as in Eurooe (HOBBS. 1975). this group of cond%ons is the most important cause of secondary IgM deficiency. Thus in an African patient detection of a serum IgM level below the normal range of people living in that area should suggest a diagnosis of malignancy, even if the serum IgM is well within the normal range of people living in developed countries.

Table - Diagnoses in 43 patients with IgM deficiency Chronic lymphatic leucaemia Lymphoma Other malignancies (hepatoma 2, myeloma 1, acute leucaemia 1 and carcinoma of the ovary 1) Schistosomiasis Cirrhosis Miscellaneous Fully investigated but not diagnosis Imcompletely investigated Total

9 6 5 4 2 6 7 4

43 -

We are, etc., Y. M. FAKUNLE M. DAMISAH A. B. AJDUKIEWICZ H. C. WHITTLE B. M. GREENWOOD The Department of Medicine, Ahmadu Bell0 University, Zaria, Nigeria.

References Cornille-Brogger, R. (1975). A case of serum IgM deficiency in an area of high endemicity of malaria (Northern Nigeria). Transactions of the Royal Society if Tropical Medicine and Hygiene, 69, 515-5 16. Hobbs. J. R. (1975). InM deficiencv. In: 1mmunodeficiency in man and &imaZs, Bergsma, D., Good, R. A., Finstad, J. & Paul, N. W. (Editors). Sunderland, Massachusetts: Sinauer Ass. Inc., pp. 112-l 16. Sagoe, A-S. (1970). Tropical splenomegaly syndrome: long-term proguanil therapy correlated with spleen size, serum IgM and lymphocyte transformation. British Medical Journal, iii, 378-382. Accepted for publication

10th July 1977

Filariasis due to Wuchereria bancrofti in Haiti SIR-In Haiti the incidence of filariasis due to Wuchereria bancrofti, though recognized since the XVIIIth Century, has only been studied by WILSON (1928) who made a preliminary study in the principal cities. During the last ten years at the Hopital le Bon Samaritan in Limbe analyses carried out for blood-carried microfilariae by Knott’s method have regularly uncovered some cases of W. bancrofti and also of Masonella ozzardi. M. ozzardi affects the coastal regions of the island, where it seems to be transmitted by Culicoides furens (RIPERT, RACCURT & DOUYON, 1976), W. bancrofti is encountered much more in the urban milieu. Epidemiologic research has been continuing in the city of Limb6 since February 1977. Limb&, in the north of Haiti, is situated at 72” 24’ W and 19” 43’ N, some 10 km from the coast, in a fertile plain of 90 km2, surrounded by steep mountains, and influenced by the torrential character of the river which runs through it. Having a tropical humid climate, the region receives an average rainfall of 2,000 mm a year, which makes it quite fertile for agriculture. Approximately 60,000 people live in the valley of Limb& The city, which lies on the left side of the river, has about 15,000 inhabitants, and is crossed at its centre by a poorly cared-for canal where water stagnates all year long. A sample of the population chosen at random has been studied by a finger-prick blood sample of volume 20 mm3 drawn between 8.00 and 10.30 p.m. The first results which we are reporting were obtained from a sample of 1,135 persons. Microfilariae of W. bancrofti were recovered from 203, an incidence of 17.9 %, of which three cases also showed M. ozzardi. Three four-year-old children and 22% of those between 10 and 14 years showed the microfilariae. After puberty, males are more frequently parasitized than the females. The people who came from houses quite close to the canal were more frequently parasitized, and to a higher degree. The pathology most frequently encountered is a lymphadenitis of the inguinal nodes in almost all of the microfilaria carriers. Less frequently, engorged lymphatic vessels (lymphoceles) were noted, and also oedema of the lower extremities, and hydrocele. Elephantiasis and chyluria which are sometimes noted in this region have not yet been found in the course of this investigation. Mosquitoes were captured by aspiration in all of the houses where there were cases of microfilaraemia. Culex pipiens fatigans was the most abundant, but Aedes aegypti and A. taen~orhynchus were also recovered. Only C. pipiens fatigans harboured filarial larvae, the dimensions and morphology of which were characteristic of W. bancrqfti. Of 100 female specimens of C. pipens fatigans, previously treated with 70 % alcohol and stained bv the method of NELSON (1958). 20 were found to be infected with W. bancrofti,. six ‘having thoracic microfilariae, one having microfilariae and first-stage larvae in the thoracic muscles, nine having first-stage larvae (short and long sausage forms), three having second-stage larvae in the thoracic muscles, and one having four third-stage larvae in the head and proboscis. Filariasis due to W. bancroftiis therefore a real problem in the cities of the north of Haiti. The parasite is also known at the present time in Cap Haitien, Port Margot, Grande Riviere du Nord, Plaisance, and Gonaives. The vector is Culexpipiensfutigans and these first results from the town of Limb& prove that there is extensive trans-