Benjamin O. Fagbemi

Heterologous antagonistic and synergistic interactions between helminths and between helminths and protozoans in concurrent experimental infection of mammalian hosts.

Experimental concurrent infection with two or more parasite species in mammalian host models may result in heterologous antagonistic and synergistic interactions ranging in magnitude from reduced/enhanced growth and fecundity to blockage/enhancement of establishment/expulsion. With some exceptions only, there is a reasonable correlation between the levels of interaction monitored by parasitological and by clinico-pathological parameters. Heterologous antagonistic interactions mediated by functional and specific immunological cross-reactivity occur between closely related parasite species exhibiting a marked immunobiological similarity. In contrast, antagonistic interactions between antigenetically more remote species of helminths, protozoan-induced resistance to helminth infection and helminth-induced suppression of concurrent protozoan infection generally appear mediated by immunologically non-specific factors like macrophage activation and inflammatory reactions. Synergistic heterologous interactions between helminths, helminth-induced enhancement of concurrent protozoan infection and interference with the development and maintenance of resistance to helminth infection in response to concurrent protozoan infection are generally thought to be mediated by non-specific parasite-induced immunosuppression. Concurrent experimental infection is very complex. There are problems and limitations in extrapolating from experimental studies on concurrent infection in laboratory animals to natural polyparasitism. This fact, coupled with the complex influence of ecological factors on the pattern and frequency of concurrent natural infection means that major consequences of natural concurrent parasite infection have not been definitively demonstrated. Appropriately planned and controlled field studies and further laboratory experiments on primate and domestic animal models are imperative for elucidation of the importance of heterologous interactions in concurrent parasite infection for the disease pattern in man and domestic stock. Experimental studies hitherto conducted on concurrent parasite infection pointing to natural heterologous interactions may be a valuable starting point for further studies.

Immunodiagnosis of fasciolosis in ruminants using a 28-kDa cysteine protease of Fasciola gigantica adult worms

A homogeneous extract of a 28-kDa cysteine protease of Fasciola gigantica adult worms was used as the antigen for immunodiagnosis of fasciolosis in cattle, sheep and goats using the Falcon assay screening test enzyme-linked immunosorbent assay technique. This antiprotease assay technique was found to be very rapid and sensitive and may be useful as a supplementary method for the diagnosis of fasciolosis in ruminants.

Detection of circulating antigen in sera of Fasciola gigantica-infected cattle with antibodies reactive with a Fasciola-specific 88-kDa antigen

Antibodies against a specific 88-kDa antigen of Fasciola gigantica were used for the detection of circulating antigen in the sera of cattle with experimental and natural infections of F. gigantica by a double antibody ELISA. Circulating antigen was detectable as early as the second and third weeks after infection and positive absorbance values were obtained for the entire duration of infection. Absorbance values decreased below the cutoff point 3 weeks after chemotherapy with oxyclozanide. This immunoassay also greatly enhanced the specificity of immunodiagnosis of fasciolosis in naturally infected cattle. The test system has excellent potential for the accurate diagnosis of ruminant fasciolosis.

Anthelmintic Activity of Extracts of Spondias mombin Against Gastrointestinal Nematodes of Sheep: Studies In Vitro and In Vivo

This study was carried out to validate the efficacy ofSpondias mombin, used locally as an anthelmintic, and to standardize the effective dose of the plant extract required for worm control in livestock. In vitro andin vivo studies were conducted to determine the direct anthelmintic effect of ethanolic and aqueous extracts ofS. mombin towards different ovine gastrointestinal nematodes. A larval development assay (LDA) was used to investigate thein vitro effect of extracts on strongyle larvae. Another study was conductedin vivo to evaluate the therapeutic efficacy of the extracts administered orally at dose rates of 125, 250, 500 mg/kg to sheep naturally infected with gastrointestinal nematodes. Twenty sheep were selected on the basis of positive faecal egg counts (750 epg). The sheep were allocated randomly to a non-medicated control group (A) or to groups given 125 mg/kg (B), 250 mg/kg (C) or 500 mg/kg (D) of extract, respectively. Sheep in groups B–D were given extracts orally on two days. Individual faecal egg counts were performed on days 0, 3, 6, 9 and 12. The presence ofS. mombin extracts in in vitro cultures of larvae decreased the survival of L3 larvae. The LC50 of the aqueous extract ofS. mombin was 0.907 mg/ml, while the LC50 of the ethanolic extract was 0.456 mg/ml. This difference in LC50 was statistically significant (p>0.05). The mean percentage faecal egg reduction of sheep drenched with 500 mg/kgS. mombin extracts was 15.0%, 27.5%, 65.0%, 65.0%, 100.0% againstHaemonchus spp., Trichostrongylus spp., Oesophagostomum spp., Strongyloides spp. and Trichuris spp. respectively, on day 12. Extracts ofS. mombin could find application in the control of helminths in livestock.

The effect of Trypanosoma brucei infection on serum biochemical parameters in boars on different planes of dietry energy

Young boars were placed on diets with either low or high dietary energy and subsequently infected with a virulent stock of Trypanosoma brucei. The effects of dietary energy level and infection on some serum biochemical parameters were evaluated up to 7 weeks post-infection (p.i.). There were no significant changes in serum electrolyte (Na+, K+) concentrations resulting from dietary energy level and/or the infection. Serum total protein and albumin levels significantly decreased in both groups of infected boars, the decline being greater in those on the low-energy diet. Infection was accompanied by a rise in serum transaminase (serum aspartate and alanine aminotransferases) levels which were higher in infected boars on the low-energy diet. The serum testosterone concentration declined in both groups of infected boars with the fall being more pronounced in the group on the low-energy diet. The results indicated that the reproductive efficiency of boars may be modulated by nutrition and that adequate feeding may assist in ameliorating the deleterious effects of trypanosomiasis on production in endemic areas.

Time-course analysis of antibody response by EITB and ELISA before and after chemotherapy in sheep infected with Fasciola gigantica

The time-course analysis of the antibody response to Fascicola gigantica infection in sheep was studied by enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunoelectrotransfer blot (EITB). Sera from sheep experimentally infected with F. gigantica were reacted with excretory-secretory antigens of the worm before and after chemotherapy with oxyclozanide. In ELISA, there was a significant increase in anti-Fasciola antibody by 2 weeks after infection and there was a sharp decrease in antibody titer by 4 weeks after treatment. By EITB, the infected sheep sera recognised four polypeptides in the range of 43-75 kDa as early as 2 weeks after infection, with more polypeptides being recognised as the infection progressed. Recognition of an 87 kDa antigen was lost by 2 weeks after treatment and is therefore a good marker for treatment efficacy. Comparative immunoblotting with sheep anti-Paramphistomum, anti-Dicrocoelium and anti-Fasciola sera revealed that the 17 kDa, 21 kDa, 57 kDa and 69 kDa proteins are specific to fasciolosis and are good antigens for early and specific immunodiagnosis of F. gigantica infection in sheep.

The isolation of Fasciola gigantica-specific antigens and their use in the serodiagnosis of fasciolosis in sheep by the detection of circulating antigens

The 17kDa and 69kDa polypeptide antigens which are specific to Fasciola gigantica were excised from polyacrylamide gels and used for the immunization of rabbits to raise monospecific antisera against these polypeptides. These sera were labelled with horseradish peroxidase and used for the detection of circulating 17 kDa and 69 kDa antigens by a direct enzyme-linked immunosorbent assay in the sera of sheep that were experimentally or naturally infected with F. gigantica. The 17 kDa antigen was detected in the sera of infected sheep as early as 1 week after infection and, following chemotherapy with oxyclozanide, negative seroconversion occurred 2 weeks later. The 69 kDa antigen was detectable as from the fourth week of infection and its detection ceased 3 weeks after chemotherapy. The serodiagnosis of F. gigantica, based on the detection of the 17 kDa antigen in sheep sera, was more specific and sensitive than that based on the detection of the 69 kDa antigen.

THE USE OF MONOCLONAL ANTIBODY FOR THE IMMUNODIAGNOSIS OF FASCIOLA GIGANTICA INFECTION IN CATTLE

Antigens that were specific to Fasciola gigantica were obtained from the whole worm homogenate of the parasite by immunoaffinity chromatography in cyanogen bromide-activated sepharose 4B columns and used for the production of monoclonal antibodies. The F. gigantica-specific monoclonal antibody was labelled with horseradish peroxidase and used for the detection of circulating antigen by the direct ELISA method in the sera of cattle experimentally infected with the parasite. Circulating antigens were detectable in the sera of the animals as from the third week after infection while negative absorbance values were obtained 2 weeks after the termination of the infection by chemotherapy with oxyclozanide. This immunodiagnostic method offers an attractive alternative as a supplement to the conventional coprological diagnosis of fasciolosis.

Molecular characterization of Cryptosporidium in children in Oyo State, Nigeria: implications for infection sources

A study was conducted to detect and identify Cryptosporidium spp. in 43 children from Oyo State, Nigeria. Using nested polymerase chain reaction, 11.6% of the children were identified as positive for Cryptosporidium spp. Restriction fragment length polymorphism analysis and DNA sequencing of the PCR products showed the presence of three subtype families of Cryptosporidium hominis (two isolates of Ia and one isolate of Ib) and Cryptosporidium parvum (two isolates of IIc), all anthroponotic in nature. This study identified a high diversity of Cryptosporidium subtypes and clearly suggested that anthroponotic rather than zoonotic transmission played a more important role in the epidemiology of Cryptosporidium in the studied area.

The purification and characterization of a cysteine protease of Fasciola gigantica adult worms

A 26-28 kDa protease was isolated from Fasciola gigantica adult worms by a two-stage purification process of column chromatography in a Sephacryl S-200 column and affinity chromatography in an L-phenylalanine-agarose column. This protease is a cysteine (thiol) proteinase with an optimum pH of 4.5 and is not inhibited by anti F. gigantica immunoglobulin G. The enzyme was inhibited by protease inhibitors known to inhibit cysteine proteases but not by metallo-, aspartate or serine protease inhibitors. The effect of several protease inhibitors and anti-F, gigantica IgG was also assessed on the total proteolytic activity of F. gigantica. There appears to be a preponderance of cysteine protease activity in F. gigantica and there was a significant inhibition of total proteolytic activity by anti-F. gigantica IgG.