Journal of Helminthology

Samples of Echinococcus granulosus from seven pigs from Mexico were compared with isolates of the parasite from pigs in Poland and representative strains and species of Echinococcus. Isolates from pigs in Mexico were found to be genetically identical to E. granulosus from Polish pigs and distinct from other major genotypes by sequencing part of the mitochondrial cytochrome c oxidase I (COI) mtDNA locus, restriction fragment length polymorphism (RFLP) of the polymerase chain reaction (PCR) amplified rDNA internal transcribed spacer (ITS) 1 using five different enzymes, and random amplified polymorphic DNA (RAPD) analysis. These results were complemented by data on hook morphology and together strengthen the view that Echinococcus maintained in a cycle involving pigs and dogs is a distinct strain that is conserved genetically in different geographical areas. The present study supports the close relationship of the cervid, camel and pig strains and raises the question of their taxonomic status.

Mô tả hình thái của lớp vỏ ngoài của bốn loài metacercariae microphallid từ giai đoạn ấu trùng cercariae xâm nhập cho đến khi trưởng thành thành metacercariae được bao bên trong vật chủ trung gian thứ hai là động vật giáp xác. Lớp vỏ ngoài của metacercariae phát triển các lá và nhú bề mặt, cùng với các túi tiết trên bề mặt, cho thấy lớp vỏ này có chức năng hấp thụ. Sự biến mất của các hạt tiết ra từ lớp vỏ ngoài đồng thời với sự xuất hiện của lớp vỏ nang đầu tiên cho thấy lớp vỏ này có vai trò trong việc hình thành vỏ nang sơ bộ. Sau đó, metacercariae tiếp tục phát triển và dường như giữ được khả năng hấp thụ của chúng. Lớp vỏ ngoài cũng tham gia vào việc vận chuyển vật chất vào khoang quanh metacercarial trước khi vật chất này trở thành một phần của các lớp vỏ trong phát triển. Có vẻ như vật chất này có nguồn gốc từ các tế bào vỏ nằm giữa các tế bào nhu mô bên dưới lớp hợp bào vỏ ngoài. Khi hoàn thành các lớp vỏ phụ, đã xảy ra sự thoái hoá dần dần của các cấu trúc liên quan đến sự hấp thụ và sự tích tụ tiến triển của các hạt dẹt dày đặc có thể được truy nguồn từ các tế bào vỏ bên dưới. Cả bốn loài microphallid (Maritrema arenaria,M. subdolum,Levinseniella brachysoma vàMicrophallus claviformis) đều thể hiện cùng một mô hình phát triển nhưng thời gian trải qua mỗi giai đoạn khác nhau tuỳ vào thời gian di chuyển đến các vị trí bao bọc. Mô hình phát triển của vỏ ngoài được mô tả được cho là áp dụng cho tất cả các metacercariae microphallid và có thể cho các metacercariae khác trải qua sự tăng trưởng và phát triển trong các vật chủ trung gian thứ hai của chúng.

The secondary response of eosinophilia has been studied in mice infected withA. suum. In mice infected orally with 1000A. suumeggs, larvae disappeared from the body within two weeks after infection. The number of peripheral blood eosinophils decreased to the pre-infection level within eight weeks. A typical secondary response of IgG antibody production to egg antigen was found after reinfection with 1000 eggs. The number of peripheral blood eosinophils increased more rapidly after reinfection than after the primary infection. However, the peak number of eosinophils after reinfection was similar to that after primary infection, and the long-lasting characteristics of eosinophilia after reinfection did not differ from those after primary infection. These results suggest that the secondary response of eosinophilia is characterized by a rapid increase in the number of eosinophils inA. suum-reinfected mice.

The indirect immunofluorescent technique was used to determine the occurrence of IgA, IgM and IgG₁immunoglobulin-containing cells in local intestinal mucosal immune responses toHymenolepis citelli, H. diminutaandH. microstomainfections in mice. In the intestinal lamina propria ofH. citelliandH. diminutainfected mice there was no increase in the mean numbers of immunoglobulin-containing cells when compared with uninfected control mice, but there was inH. microstomainfected mice. The numbers of IgG₁– positive cells in both infected and uninfected mice were very small relative to IgA and IgM immunocytes. The distribution of immunocytes in the lamina propria of infected and uninfected mice was essentially similar and the localization of isotypes in duodenal sections showed no immunoglobulins in the villous epithelial cells. There was also no marked difference between primary and secondary infections indicating that immunoglobulin-containing cells play no major role in functional immunity against hymenolepid infections in the mouse. The presence of IgA and IgM was also demonstrated on the tegument of the tapeworms, although the distribution was patchy and more abundant onH. microstomathan onH. diminutaorH. citelli. The time of appearance of both isotypes was latest onH. citelli.

A sandwich ELISA method using previously described E/S antigen-specific monoclonal antibodies has been developed to detect circulating immune complexes in patients infected with Toxocara canis. This technique could be used for the study of the dynamics of the parasite-host relationship, as we believe the detection of immune complexes and/or soluble antigen to be an improvement over detection of antibodies only. In this parasitosis, antibodies may be present in residual levels for prolonged periods after active infection.

Infection with Oesophagostomum sp. appears to be extremely common in man in northern Togo and Ghana Adult specimens were recovered from the intestinal lumen by treatment with pyrantel pamoate and the morphological characteristics of oesophagostomes of man could for the first time be compared with information available on the morphology of oesophagostomes of monkeys. The observations and measurements demonstrated that the species involved is Oesophagostomum bifurcum and that the eggs of this species cannot be differentiated from those of Necator americanus. Both infections occur simultaneously in the population involved. The L₁ larvae, too, cannot be differentiated from hookworm L₁ larvae. The L₃ however, are characteristic. Diagnoses of human Oesophagostomum infections is based on the detection of these larvae in coprocultures. In the present paper, the eggs, the L₁ and L₃ larval stages and the adults, carefully described and photos are given.

Oesophagostomum bifurcum larvae, cultured from human stools collected in northern Ghana, were used to establish experimental infections in monkeys. A patent infection was established in a rhesus monkey (Macaca mulatta) and this infection was used to generate larvae to inoculate additional monkeys. In all, 17 animals were inoculated. Thirteen of 15 animals developed antibodies to the infection between 19 and 62 days post inoculation (PI); two animals had a positive response before inoculation. Four of ten animals developed patent infections between 88 and 134 days and passed eggs in the faeces. Egg shedding was consistent in only one animal, but at low levels of one or two eggs per 2 mg direct smear, and extended over a 400 day period. In the other three animals, egg shedding was sporadic and of only 2–4 weeks duration. In seven animals necropsied between 19 and 22 days PI, one to 17 early fourth-stage larvae were recovered from nodules in the bowel wall; in an eighth animal examined at 314 days, six immature adult worms (early fifth stage) were recovered from nodules in the bowel wall. The morphological features and growth of these recovered larvae are described. Three animals were inoculated with larvae that had been dried for one week at 28°C; two animals began shedding eggs at 128 and 134 days PI, respectively. The present results suggest that the parasite obtained from humans is poorly adapted to lower primate hosts, and supports the concept that Oesophagostomum bifurcum found in humans and monkeys in the same geographical region of northern Ghana and Togo are distinct and that the infections in humans are not likely to represent zoonotic infections acquired from monkeys.

The reliability of different egg counting methods for estimating the intensity of Trichostrongylus tenuis infections in red grouse, Lagopus lagopus scoticus, was investigated in the autumn, when grouse may harbour high parasite intensities. Possible limitations to the use of these methods were also examined. Faecal egg counts were found to accurately estimate T. tenuis worm intensities, at least up to an observed maximum of c. 8000 worms. Two egg counting methods (smear and McMaster) gave consistent results, although the exact relationship with worm intensity differed according to the method used. Faecal egg counts significantly decreased with increasing length of sample storage time, but egg counts were reliable for estimating worm intensity for three weeks. The concentration of eggs in the caecum was also found to reliably estimate worm intensity. However, egg counts from frozen gut samples cannot be used to estimate worm intensities. These results conclude that, despite some limitations, faecal and caecum egg counts provide useful and reliable ways of measuring T. tenuis intensities in red grouse.

The model of Onchocerca lienalis microfilariae (mf) injected into inbred CBA/Ca mice was studied for its usefulness as an additional primary/secondary drug screen for onchocerciasis. Invermectin, DEC, suramin, flubendazole, mebendazole, levamisole, Mel W, furapyrimidone, metrifonate, amoscanate and the new Ciba-Geigy compounds CGP 6140, CGP 20'376 and CGI 17658 all significantly reduced levels of mf at a dose of 5x100 mg/kg or less. An early dosing protocol, on days 3–7 after infection, was found to be generally more effective than dosing on days 11–15, followed by necropsy on day 18. In some cases there were important differences in levels of drug activity depending on whether the drug was administered by the subcutaneous or oral route, indicating that new compounds should be tested via both routes. Ivermectin was by far the most active compound examined, virtually clearing mf from the skin at a dose of 5x0.0063 mg/kg and producing a significant mf reduction (63.5%) at 5x0.008 mg/kg following subcutaneous administration. In comparison, DEC was much less active, producing a 32.4% mf reduction at 5x25 mg/kg ranging up to a maximum of 72% reduction at 5x100 mg/kg. CGI 17658 was the most active compound examined next to ivermectin, almost 100% effective against skin mf at a dose of 5x6.25 mg/kg via the oral route while being less effective via subcutaneous administration (65% reduction). The lowest effective dose examined was 5x3.13 mg/kg (per os) which reduced mf levels by 64%. CGP 20'376 was also very active, resulting in a 46% (subcutaneous) and 62% (per os) reduction at a dose of 5x6.25 mg/kg. This mouse model has clearly identified all the known microfilaricides examined and also, to a lesser extent, those compounds considered to be principally macrofilaricides. We believe it has value as an additional drug screen for onchocerciasis, which will enable the evaluation of novel compounds against skin-dwelling Onchocerca mf at the primary/secondary level, providing complementary information to new in vitro screens using adult Onchocerca.