Omar O. Barriga
Ohio State University
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Veterinary Parasitology | 1988
Omar O. Barriga
The visceral infection of humans with Toxocara canis is particularly prevalent in children and may cause a variety of symptoms that commonly persist for 6-24 months. The ocular infection usually causes permanent loss of visual acuity. Human infection is acquired by ingestion of embryonated T. canis eggs with contaminated dirt. Review of recent reports indicates that patent T. canis infection is widely prevalent in the general population of dogs all over the world (3-81%) and results in a substantial contamination of the ground (0.3-87%). The results of sensitive and specific serological tests suggest that about 7% of the clinically healthy human population of the United States, about 5% of that of Canada, and about 4% of that in Great Britain is infected with the parasite. Control of transmission of the parasite to man is often attempted by eliminating the infection in dogs, reducing the population of dogs and the environmental contamination with their feces, and educating the public about the zoonotic potential of toxocariasis. The evidence reviewed indicates that these methods are only marginally effective. Because T. canis relies on congenital and lactogenic transmission to persist in nature, only a procedure that effects the sustained killing of the reservoir larvae in the tissues of the bitch, or of newly-acquired parasites, is expected to be successful. Research with mice, rabbits and dogs demonstrated that prior infections of the host induce the development of protective immunity to reinfections. This procedure, however, leaves remnant populations of larvae from the immunizing infections that are resistant to anthelmintics and to the effect of prior irradiation. Hyperimmunization with partially-purified extracts of T. canis larvae induced 37% resistance to a challenge in mice when the extract was administered alone, and 76% resistance when administered with lipopolysaccharide adjuvant. Production of complete resistance, however, will probably require the prior control of the immunosuppression induced by the parasite. T. canis infections inhibit the production of homologous protective immunity and antibody responses to heterologous antigens, probably by interfering with the activity of helper T-cells, competing with protective antigens, and suppressing antibody synthesis. The evidence indicates, however, that an anti-T. canis vaccine to eliminate the parasite in dogs is feasible.
Veterinary Immunology and Immunopathology | 1992
Omar O. Barriga; Nahad W. Al-Khalidi; Sharron L. Martin; Milton Wyman
Three clinically normal beagles, 3 beagles with localized demodectic mange (LDM), and 3 beagles with generalized demodectic mange (GDM) were investigated simultaneously 1-3 and 4-6 weeks from the appearance of the clinical signs. Blood clinical examination and reactivity of peripheral lymphocytes to Con A and PHA were investigated in the first instance, and reactivity to Con A, PHA, and LPS in the second. Eight aliquots were used in each blastogenesis assay for each dog. All dogs were negative for rheumatoid factor. The results of blastogenesis showed that many observations were distributed non-normally, and that not all dogs in each group responded homogeneously. Comparison of blastogenesis results between dogs demands careful statistical analysis. Responses to mitogens were normal in all dogs at 1-3 weeks except for the LDM dogs that showed an increased response to PHA. Only the response to Con A was moderately inhibited in the LDM dogs at 4-6 weeks. All responses were severely depressed in the GDM dogs at 4-6 weeks. This means that immunosuppression follows rather than precedes the clinical manifestations of GDM, and implies that the phenomenon is induced by the parasite or the hosts reaction to it.
Veterinary Parasitology | 1984
Omar O. Barriga
There is current evidence that infections with Trichinella spiralis, Ascaris suum, Nippostrongylus brasiliensis, Nematospiroides dubius (syn. Heligmosomoides polygyrus) and diverse filariae affect the immune responsiveness of their hosts. T. spiralis, or its extracts, can depress or enhance the heterologous humoral or cell-mediated immunities, and affect macrophage activity or the response to other invaders. These effects are induced by products of the migratory and early muscle larvae and appear to obey more than one single-mechanism. A suum acute infections or extracts depress responses involving T cell activity, but stimulate polygonal expansion of B-cells. Nippostrongylus brasiliensis causes polyclonal stimulation of IgE-producing cells, enhances immune responses during the first week of infection and inhibits them later on. Nematospiroides dubius depresses homologous and heterologous immunity and facilitates the permanence of other intestinal nematodes. Filarial worms appear to depress the homologous cell-mediated immunity and the heterologous humoral response by induction of suppressor cells and humoral factors. These phenomena are probably the result of evolutionary pressures on the parasites that facilitate their survival. In the host, they are likely to aggravate the homologous infection, facilitate intercurrent conditions and interfere with immunoprophylaxis procedures.
Journal of Parasitology | 1991
Omar O. Barriga; Francisco Andujar; Witold J. Andrzejewski
Three sheep were infested 4 times with 100 Amblyomma americanum tick pairs and kept indoors until the natural termination of the infestations. Characteristics of the tick populations that show efficiency of feeding, fertility, and offspring development, and ELISA antibodies to tick salivary gland extracts were studied at each infestation. On average, female ticks fed on tick-naive sheep detached at 12.1 +/- 0.2 (mean +/- standard error) days, weighed 492 +/- 16.8 mg, engorged 40.7 mg per day, and 35% survived to detachment during the first infestation. During the fourth infestation, they detached at 17.3 +/- 0.8 days, weighed 321 +/- 14.4 mg, engorged 18.8 mg per day on average, and 23% survived to detachment. On average, oviposition of female ticks fed on tick-naive sheep started at 11.8 +/- 0.6 days of detachment, the egg mass weighed 236 +/- 13.2 mg, 43% of the female weight turned into eggs, and 89% of the ticks that detached survived to oviposition during the first infestation. During the fourth infestation, oviposition started at 15.1 +/- 0.5 days, the eggs weighed 103 +/- 9.9 mg, 13% of the tick weight became eggs, and 67% of the ticks survived to oviposition. On average, eclosion started at 35.4 +/- 0.9 days of oviposition and 83% of the egg batches hatched in the first infestation. During the fourth infestation, eclosion started on day 34.9 +/- 0.7, and 47% of the egg batches hatched. Anti-tick resistance was expressed as an inhibition of feeding, fertility, and offspring development.(ABSTRACT TRUNCATED AT 250 WORDS)
Veterinary Immunology and Immunopathology | 1986
Omar O. Barriga; Nahad W. Al-Khalidi
Twenty-one parasite-naive dogs were infected with 60,000 protoscolices of Echinococcus granulosus. Transformation of peripheral lymphocytes was investigated before and 29 days after the infection, immunoglobulin concentration and anti-hydatid fluid protein (HFP) titers in serum and feces before and at 35 days of infection, skin reactivity to HFP at 36 days, and characteristics of the parasites at 40 days. The infection caused a significant depression of the spontaneous, lipopolysaccharide-stimulated, and purified protein derivative-stimulated blastogenesis. Responses to phytohemagglutinin were unchanged and reactivity to concanavalin A was enhanced with the infection. Only the concentrations of IgG and IgA in the serum and IgA in the feces increased significantly after infection. Fifteen (71%) dogs produced significant serum titers of anti-HFP hemagglutinins but copro-antibodies were detectable in only 3 dogs at minimum titers. Titers were abolished by treatment with 2-mercaptoethanol. The serum of 11 (52%) dogs transferred passive cutaneous anaphylaxis to guinea pigs but none transferred skin reactivity to pups or rabbits. Five and 1 (but not 0.2) micrograms of HFP caused skin reactivity in 4 parasite-naive dogs. Nineteen (90.5%) infected dogs reacted significantly to skin inoculation of 0.2 microgram of HFP at 0.5 hours and 13 (62%) at 6 hours. The 7 dogs with the highest anti-HFP serum titers or the greatest skin reactivity at 6 hours had significantly less mature or fewer tissue parasites, respectively, than the 7 dogs with the smallest responses. Since there was evidence that the specific immunity was still developing at the time of the study, these results indicate that immunological diagnosis of, and artificial immunization against, canine echinococcosis are feasible.
Veterinary Parasitology | 1995
Omar O. Barriga; Sergio Silva Da Silva; Joao S.C. Azevedo
Six tick-naive male Hereford calves were infested once a month for 6 months with 18,000 Boophilus microplus larvae on the back and with 400 larvae in a cloth bag glued on the lumbar region. Working with the bag ticks, 12 tick characteristics were recorded for each infestation. Each tick attribute was analyzed for significant differences with those of the first infestation (analysis of variance), and for similarity (clustering), degree of relationship (correlation), and concomitant variation (regression) against all the other attributes during the first, third, and sixth infestations. Some attributes were affected maximally by host immunity about the third infestation but recovered later (length of feeding, detachment weight, egg weight, start of oviposition, fertility efficiency index), whereas others continued to be affected until the last infestation (length of oviposition, corpse weight, start of hatching, feeding efficiency index). All analyses showed that weight at detachment and egg weight were closely related, and corpse weight was partially related to these two. All other natural characteristics were largely independent. Length of feeding showed no significant relation with weight at detachment nor length of oviposition with egg weight. These findings suggest that different tick functions are independently affected by host immunity and recommends against estimating general anti-tick resistance by the evaluation of only a few tick characteristics.
Veterinary Parasitology | 1986
Aristides Lazo; Omar O. Barriga; Donald R. Redman; Steen Bech-Nielsen
Soluble and particulate fractions of Cryptosporidium sp. oocysts from cattle were obtained by homogenization and sonication. Electrophoresis of the soluble fraction in polyacrylamide gels with sodium dodecyl sulfate and silver staining revealed the presence of 41 bands. Enzyme-linked immunosorbent assay (ELISA) of sera from rabbits immunized with either fraction and from a calf 40 days after infection showed that the animals produced specific antibodies. Enzyme-linked immunoelectrotransfer blot tests revealed the presence of five antigens with the rabbit sera and nine with the calf serum. ELISA proved to be an appropriate test for diagnosis of cryptosporidiosis. Selection of reactive antigens may improve the quality of diagnosis and/or reveal the presence of protective materials in the parasite.
Veterinary Parasitology | 1981
Omar O. Barriga; Jose V. Arnoni
Abstract Four groups of 5 40-day-old, Eimeria stiedai -naive, New Zealand rabbits were infected with 0 (Group A), 10 2 (B), 10 3 (C) and 10 4 (D) sporulated oocysts of E. stiedai and observed for 50 days. Serum glutamic pyruvic (GPT) and glutamic oxalacetic (GOT) transaminases, bilirubinemia, lipemia, proteinemia, glycemia, oocyst output, body, carcass and liver weights, and mortality were recorded. Four physiopathological events were identified: (1) a phase of indirect damage to the hepatocytes that takes place during the first 2 weeks of infection and is characterized by increased transaminases; (2) a cholestatic period consequent to the production of oocysts that begins suddenly in the 3rd week, diminishes gradually towards the 7th week, and is characterized by a rise of bilirubinemia and lipemia; (3) a stage of metabolic dysfunction that begins in the 3rd–4th week, intensifies for the next 3 weeks and starts to recover during the 7th week. It is characterized by hypoproteinemia and hypoglycemia; (4) a period of immunodepression characterized by the inability of the heavily infected host to inhibit oocyst production. Apart from the cholestatic phase, the respective pathogenic mechanisms remains to be studied.
Experimental Parasitology | 1979
Omar O. Barriga; Jose V. Arnoni
Abstract Groups of 5 (38–40 days old) Eimeria stiedae-naive rabbits were infected with 0 (mock infection), 102, 103, 104, and 105 sporulated oocysts of Eimeria stiedae (groups A, B, C, D, and E, respectively) and body weight, oocyst output, serum glutamic pyruvic and serum oxalacetic transaminases, bilirubinemia. lipemia, glycemia, and proteinemia were measured on diverse occasions for 50 days. Mortality and carcass and liver weights at the end of the experiment were also recorded. Mortality was 80% in group E, 40% in group D, and 0% in the other groups. Reduction of weight gain was observed from the 8th day of infection and actual loss from the 15th day in infected animals. On Day 50, the average body and carcass weights of all infected rabbits were 71.2 and 63.2%, respectively, of group A. Only groups D and E had absolute hepatomegaly and group C had relative liver enlargement. Patency and rate of increase of oocyst output were not related to dose but peak and declination of oocysts production were delayed in proportion to the infective dose. Serum glutamic pyruvic and glutamic oxalacetic transaminases were increased from Day 8 to Day 36, bilirubinemia and lipemia augmented from Day 22, and glycemia and total serum proteins decreased from Days 22 and 29, respectively. Bilirubinemia tended to recover sooner (toward Day 50) in rabbits with lighter infection and lipemia recovered from Day 36 in proportion to the size of the infective dose. Modifications of glycemia and total proteinemia were consistent but reached statistical significance only occasionally. The asexual reproduction of the parasites caused transient damage to the hepatocytes during the second week of infection, and later sexual stages altered the ductal epithelium from the fourth week.
Veterinary Parasitology | 1997
Hamid Sahibi; Adbelkebir Rhalem; Omar O. Barriga
Tick concealed antigens have been successful in producing immunity that inhibits tick fertility, but require periodic revaccination and are little effective in preventing tick feeding, which is critical to stop pathogen transmission. Tick natural salivary antigens also induce important immunity, but revaccination may be unnecessary in enzootic areas. In addition these antigens may inhibit tick feeding. We immunized groups of three tick-naive calves with four prior infestations with Hyalomma marginatum marginatum, a salivary extract (SE), or an intestinal extract (IE) of the ticks. The calves were challenged with 100 pairs of homologous ticks and characteristics representing tick feeding or fertility were recorded and compared between groups. The percentage of attachment was inhibited by 46% by the infestation-generated immunity, 47% by the SE-generated immunity, and 0% by the IE-generated immunity. The percentage of engorgement was reduced 40% by the infestations, 57% by the SE, and 29% by the IE. The length of feeding was prolonged 92% by the infestations, shortened 44% by the SE, and not affected by the IE. The weight of the engorged females was decreased 67% by the infestations, 64% by the SE, and 31% by the IE. The percentage of engorged ticks that oviposited was inhibited 52% by the infestations, 27% by the SE, and 63% by the IE. The preoviposition period was prolonged 160% by the infestations, 80% by the SE, and 140% by the IE. The egg weight was reduced 60% by the infestations, 60% by the SE, and 66% by the IE. Taking into account mortality before oviposition, fertility was inhibited 88.2% by the infestations, 87.5% by SE, and 91.4% by the IE. The effect of IE immunization on tick feeding was not significant statistically.