Trypanosoma brucei: influence of host strain and parasite antigenic type on infections in mice

Inbred mice were infected with cloned populations of Trypanosoma brucei brucei Lister S42 under carefully controlled conditions. The course of infection was found to depend both on host strain and the antigenic type of the infecting organisms. The two antigenic types used, “NIM2” and “NIM6” had differing virulence for (CBA/H × C57BL/6)F₁ mice, and when mice were infected with parasites of one clone, trypanosomes of the other type frequently appeared after the initial population had been eliminated. Different mouse strains had varying susceptibility to clone NIM6. In most cases there was an inverse relation between the survival time and the parasite load during the first peak of parasitemia. The differences in resistance to T. brucei were unrelated to H-2 haplotype: C57BL/6 and (CBA/H × C57BL/6)F₁ were most resistant, CBA/H, BALB/c and DBA/2 less so, and C3H/He most susceptible.     

Caenorhabditis elegans and Ascaris suum: inhibition of isocitrate lyase by itaconate

The largest forms of isocitrate lyase from Caenorhabditis elegans and Ascaris suum of 543,000 and 549,000 daltons, respectively, can be purified from three- to five-fold in excellent yield by pelleting from extracts at 160,000g for 4 hr. Isocitrate lyase in the pellet is much more stable toward proteolysis. Itaconate which both inhibits isocitrate lyase and suppresses the level of this enzyme in bacteria inhibits the partially purified isocitrate lyase from both C. elegans and A. suum. The inhibition is noncompetitive with respect to d_s-isocitrate at one itaconate concentration. The K_i values at 30 C, pH 7.7, are 19 and 7.3 μM for the enzyme from C. elegans and A. suum, respectively. Itaconate inhibits the growth of C. elegans in random axenic as well as monoxenic cultures. At a concentration of 10 mM, itaconate is more effective in the inhibition of random axenic cultures than is oxalate, maleate, or succinate. At 60 mM itaconate, reproduction of C. elegans larvae is completely abolished.     

Trypanosoma brucei: renal pathology in rabbits

Rabbits experimentally infected with Trypanosoma brucei S42 develop two significant renal lesions: an early proliferative glomerulonephritis associated with glomerular deposits of IgG, IgM, and β₁C laid down in a granular pattern in the glomerular capillary wall as revealed by immunofluorescence, and tubular atrophy with changes in enzyme activity of proximal tubule cells occurring late in infection. It is suggested that the two lesions could have a different aetiology. The glomerular changes result from deposition of soluble trypanosome immune complexes, whereas the tubular changes are typical of tissue ischemia. Trypanosomiasis in the rabbit could be a valuable model for studies of the pathogenesis of renal damage in Rhodesiense sleeping sickness.     

Trypanoplasma salmositica: experimental infections in rainbow trout, Salmo gairdneri.

Trypanoplasma salmositica was successfully cultured in Hanks' medium with 10% heated fetal calf serum. The culture forms were morphologically similar to blood forms and were infective to rainbow trout by inoculation. T. salmositica produced a disease in experimentally infected rainbow trout (Salmo gairdneri). The clinical signs were anemia, exophthalmia, abdominal distension with ascites, and splenomegaly. These clinical signs were observed in fish that were infected with three substrains (field substrain, cultured substrain, and cloned substrain) thus satisfying Koch's postulates. The anemia was microcytic and hypochromic and was coincident with increasing parasite number in the blood. The hemoglobin in the infected fish dropped from a normal of about 6 g% to about 1 g% in the first 10 weeks postinfection. Similarly, the hematocrit and red cell count declined as the infection progressed. Abdominal distension and exophthalmia was obvious 10 weeks postinfection. Up to 5 ml ascites fluid were recovered from each of three fish. The fluid contained large numbers of Trypanoplasma and macrophages. Some of the macrophages were engulfing the Trypanoplasma. At about this time the spleen in the infected fish was enlarged 5 to 10 times over that of control fish. The hematocrit centrifuge technique was less sensitive than wet mount examinations for the detection of the organism in blood. Fluctuations in parasite number during the course of infection may be due to antigenic change by the parasite to evade the host immune system.     

Ascaris suum and Toxocara canis: Egg extract antigens in guinea pigs and the macrophage migration inhibition test

Guinea pigs immunized with 500 μg of either Ascaris suum or Toxocara canis egg extracts, emulsified with Freund's complete adjuvant, were skin tested with both the homologous and heterologous antigens. Cross-reactions were observed in both groups. Migration of macrophages from sensitized animals was more inhibited by homologous than by heterologous antigens. Lymph-node lymphocytes from sensitized animals were stimulated to incorporate [⁸H]thymidine similarly by both antigens.     

Reversible inhibition of hatching of infective eggs of Ascaris suum (Nematoda)

Hurley L. C. and Sommerville R. I. 1982. Reversible inhibition of hatching of infective eggs of Ascaris suum (Nematoda). International Journal for Parasitology12: 463–465. Dilute solutions of an oxidising agent, iodine, reversibly inhibit hatching of infective eggs of Ascaris suum. The capacity to hatch is restored by exposure to reducing agent, hydrogen sulphide. These observations add to known similarities between hatching of infective eggs and exsheathment of infective larvae. It is proposed that the regulatory mechanisms for both processes are similar.     

Presence of chitinase in adult Varroa destructor,an ectoparasitic mite of Apis mellifera

The enzyme spectrum of an ectoparasitic mite of the honeybee,Varroa destructor (Anderson and Trueman) was studied usinga semi-quantitative method, especially designed for complex samples which havenot been purified. Exopeptidases and phosphatases are shown present. Achitinaseand enzymes able to transform carbohydrates are also present with a largerange in the intensity of the reaction. The role of the chitinase can berelatedto the supply of nutritional needs or/and the piercing and sucking behaviour ofthe adult parasite. Chitinase activity could be one factor influencing thebalance between the parasite and its host.     

Short report on the effect of a parasitic isopod on the reproductive performance of a shrimp

The present work studied the degree of inhibition caused by the bopyrid isopod Eophryxus lysmatae (Caroli, 1930 [Caroli, E., 1930. Notizia di tre specie nuove ed una poco nota di Bopiridi addominali, parassiti di Caridei del golfo di Napoli. (Contributo alla conoscenza del genere Phrixus Rathke). Boll. Soc. Nat. Napoli 41, 258-269]), an abdominal parasite, on the reproductive performance of its host, the protandric simultaneous hermaphrodite shrimp Lysmata seticaudata (Risso, 1816). Parasitized shrimp (PS) was not able to produce embryos, although they could successfully fertilise the eggs of unparasitized shrimp (US). All US paired with PS were able to fertilise eggs when paired with other US. The average number of larvae (±S.D.) produced by US shrimp paired with US and PS (344±27 and 346±23, respectively) was not significantly different (p=0.73). The average intermolt period duration (±S.D.) for US and PS (10±1.2 and 11±0.8 days, respectively) was not significantly different (p=0.82), with bopyrid parasites molting synchronously with their host. No PS lost its parasite during ecdysis. Although only three parasitized shrimp were used in the present work, parasitic castration induced by E. lysmatae seems to only affect the female sexual system of the simultaneous hermaphrodite L. seticaudata, and therefore parasite-induced “reproductive death” does not occur in this species as in other gonochoric and sequencial hermaphroditic caridean shrimp. Nutritional drain and disruption of endocrine mechanisms possibly caused by the bopyrid parasite are discussed.     

Occurrence of Amoebophrya spp. infection in planktonic dinoflagellates in Changjiang (Yangtze River) Estuary,China

The parasitic dinoflagellates in the genus of Amoebophrya can infect broad ranges of planktonic dinoflagellates, and transform algal biomass into organic matter that can be recycled within the planktonic community. The ecological significance of Amoebophrya spp. during harmful algal bloom (HAB) events was gradually recognized along with revelation of its host specificity and diversity in picoplankton communities. The eutrophicated coastal waters of China are frequently affected by HABs, particularly in Changjiang (Yangtze River) estuary and the adjacent East China Sea; while, no research has been conducted to explore the ecological roles of parasitism during HAB events and the related dinoflagellate bloom dynamics. For the first time, we confirmed the presence of Amoebophrya infections in the planktonic community of this region; six species of dinoflagellates were infected, including Ceratium tripos, Scrippsiella trochoidea, Gonyaulax spinifera, Gymnodinium sp., Gonyaulax sp. and an Alexandrium sp. Molecular sequences retrieved from environmental water samples revealed high genetic diversity of Amoebophryidae-like organisms in the water column. Amoebophrya-infected dinoflagellates were only observed in high salinity (>20) stations suggesting that salinity may be a factor limiting the distribution of Amoebophyra infections in natural environment. Whereas, no evidence of Amoebophrya infection was observed in the bloom-forming species Karenia mikimotoi, suggesting that K. mikimotoi in this region was likely free of Amoebophridae infection.