The pathology of Trypanosoma vivax (stock Y-486) in East African goats (Galla cross Masai) and Friesian cattle was studied sequentially. In both goats and cattle parasitaemia was detectable six to seven days after inoculation with 1 X 10(5) trypanosomes. The goats were more susceptible than cattle as indicated by higher parasitaemias, more severe anaemia and death in 25 per cent of the goats. The major pathological changes occurred in the lymph nodes, spleen, eyes, pituitary gland, testicles and heart. There was marked, generalised lymph node enlargement associated with an increase in the number and size of lymphocytic follicles accompanied by germinal centre formation. The medullary cords of the lymph nodes were distended and distorted by the high population of plasma cells. Similar changes were noted in the spleen. However there was no evidence for extramedullary erythropoiesis in both organs. Inflammatory changes were noted in the eyes, pituitary glands, testicles and heart.

Sera from cattle infected with three Trypanosoma congolense clones (ILNat 2.1, ILNat 3.1 and ILRAD 588) derived from different stocks were analysed for the presence of specific antibodies against the surface glycoproteins (VSGs) of the infecting trypanosomes using the solid and liquid-phase radioimmunoassays and the neutralization of infectivity test. High levels of IgM, IgG1 and IgG2 antibodies against the VSGs of the infecting variable antigen types (VATs) as well as other VATs that arose during the course of infection were detected. In addition, 11 out of 12 infected animals showed recurrent peaks of antibody activity against the infecting trypanosomes. The recurrent peaks of antibody activity against the VSGs of the infecting organisms would suggest either a reappearance of trypanosomes of the infecting types or emergence of organisms that bear similar surface determinants. In contrast to the studies on murine trypanosomiasis, there was little or no antibody activity against 2,4,6-trinitrophenylated bovine serum albumin (TNP-BSA) in sera from these cattle.

SUMMARYA herd of 20 cattle was introduced on a ranch in Kilifi, Coast Province of Kenya, where they were in contact withGlossina austenifor 6 months. In total, 65 trypanosome isolates were made from these animals. Examination of the isolates revealed that 61 wereTrypanosoma congolenseand 4 wereT. theileri. Out of the 61T. congolenseisolates, 55 were successfully passaged and cloned in mice to provide trypanosome populations for further analyses. The stocks and their clones were inoculated into goats on which teneralG. morsitans centraliswere later fed in order to provide metacyclics for use in serodeme analysis. Identification of serodemes was carried out by indirect immunofluorescence and neutralization using antimetacyclic hyperimmune sera prepared in mice against metacyclics of cloned trypanosome populations. So far 4 serodemes have been identified in 8 stocks and 7 clones. Each of the 9 stocks contained a mixture of at least 2 of the 4 serodemes identified. Furthermore, stocks isolated sequentially from individual animals contained the same serodemes despite repeated treatment with a curative dose (6 mg/kg body weight) of Berenil between isolations. From the latter finding, it can be inferred that the 4 serodemes were present on the ranch throughout the study period.

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Abstract. Prim a ry a nd seco ndary in fections of F. hepatica in mice were co m pa red to determine how prior exp osure to th e parasite affected host respo nse. Mice wit h primary pa ren chym al Fasciola infe ction s initially ha d hemo rrh agic tun ne ls filled wit h infl am matory cells a nd co nnective tissue . These lesion s were progressive and became most severe 30 days after exposure as the pa rasites entered the bile d ucts. At this time there was much hype rpla sia and thick ening of all layer s of th e d uct system nea r the parasites a nd occasiona lly severe periportal fibrosis. By 2 months aft er ex posure regen erat ion of the da mage d liver cells was complete although hyp erpl asia persisted in bile d ucts co ntaini ng fluk es. In mice with seco nda ry infec tio ns (mice exposed 40 to 50 days afte r first infectio n), the infla m ma tory resp on se was faster a nd shorter. Most lesion s were resolv ed by 30 days afte r th e seco nd expos ur e. There was littl e differen ce in histology of primar y a nd seco ndary infections during the chro nic ph ase of the disea se.T he ec o n o mic importa nce of Fasciola hepatica to the li vest ock in d us t ry has stim u la ted re searc h o n m an y a spects o f this p a ra site [I ]. A m o n g th ese, the sea rc h fo r a su ita b le labo rato ry h ost h a s received much a ttention and in fec tio ns in m ice , ra ts, [4][5][6]13], catt le [8] a n d sh ee p [9]. The p athoge n esis o f second a ry in fec tio ns h a s rece ived le ss a tt e n tio n , pa rt icularly in mice , a n d co m pari sons of the lesions p roduced in suc h infecti o n s in m ice a n d ruminants h a ve not been m a d e . Materials and Meth odsTh e stra in of mice a nd parasite , and meth od s for produ cti on of metacercari ae a nd infe ction have been described [ 13,16]. We establish ed prima ry in fectio ns by giving two metace rcari ae to eac h of 120 adu lt ma le mice. T hese were d ivided into fou r gro ups of 30 eac h (gro up s I-I V).70 3