Renal involvement in mice experimentally infected with Toxocara canis embryonated eggs.

Histological examination of kidneys from mice experimentally infected with Toxocara canis embryonated eggs demonstrated the presence of a segmental or diffuse mesangioproliferative glomerulonephritis. Immunohistochemical studies established that renal alterations were associated with glomerular deposits of IgG, IgM and third component of complement (C3). These findings suggest that an immunomediated mechanism might possibly be involved in the genesis of kidney damage observed in mice infected with T. canis embryonated eggs.     

Effect of fenbendazole on Toxocara canis larvae in tissues of infected dogs.

The effect of fenbendazole therapy was studied in six dogs fed 10,000 embryonated Toxocara canis eggs. At 47 days after they were fed T canis, four dogs were given fenbendazole in two divided doses totaling 50 mg/kg of body weight each day for 14 days. Two infected dogs were not given fenbendazole. All dogs were necropsied at the end of treatment and the foci were counted in the lungs; their skeletal muscles were digested in 1% trypsin for the recovery of larvae. The T canis larvae were not recovered from the skeletal muscle of the four infected dogs treated with fenbendazole; 15 and 42 larvae/100 g of skeletal muscle were recovered from the two nonmedicated infeected dogs. The number of grossly visible foci on surfaces of lungs in treated dogs was markedly less than in the nonmedicated infected dogs. The results indicate that fenbendazole might be effective in preventing prenatal infection in dogs.     

The effect of radiation on the viability and migratory ability of second-stage larvae of Toxocara canis in mice

Larval counts were made on mice 2 days after oral inoculation with X-ray (0-320 Krad) or of gamma ray (0-6 Mrad) irradiated eggs containing second-stage Toxocara canis larvae. The majority of the larvae irradiated with 0-40 Krad were recovered from the liver and lungs, while most of the larvae irradiated with 80 or 160 Krad remained in the digestive tract, mainly in the stomach and the proximal half of the small intestine. Only a small number of the 320 Krad irradiated larvae was recovered from the mice. No significant difference was observed in the viability of irradiated larvae incubated in vitro up to 13 days after irradiation. However, a substantial percentage of the 160 and 320 Krad-irradiated larvae hatched during that period. Very few larvae were recovered from the digestive tract of mice inoculated with eggs irradiated with 0.5 Mrad, and only one and four larvae were recovered from the liver and lungs of a mouse. No visceral larval migration was observed in mice inoculated with 1 Mrad-irradiated eggs. The minimum lethal radiation dose for second-stage T. canis larvae in eggs is proposed to be 1 Mrad.     

Toxocara cati larvae persist and retain high infectivity in muscles of experimentally infected chickens

The distribution of Toxocara cati larvae in the organs of chickens (n=31), experimentally inoculated with 3000 embryonated eggs, was examined 1, 2, 3, 7, 29, 86 and 175-176 days post-infection (dpi), and the infectivity of recovered larvae was evaluated by bioassay in mice. The duodenum, liver, lungs, heart, brain, pectoral muscles (white meat), and hindlimb muscles (red meat) of the chickens were HCl-pepsin digested for larval recovery. Larvae were recovered from all chickens [mean=220.4 ± 114.9 (SD)], and although no decrease of total larval recovery was observed over time, predilection sites changed: liver (92.6% of larval recovery) at 1 dpi; lungs (77.3%) and liver (20.9%) at 2 dpi; lungs (80.8%), muscles (9.4%), and liver (8.5%) at 3 dpi; muscles (52.0%) and lungs (45.6%) at 7 dpi, whereafter most larvae were recovered from muscles: 29 dpi (99.5%), 86 dpi (99.3%) and 175-176 dpi (99.6%). In the bioassay, 52.9% of larvae from 175 to 176 days old infections in chickens established in mice, which demonstrates that T. cati larvae retain infective in the muscles of chickens for half a year. These results highlight the zoonotic potential of poultry meat as a causative agent of human toxocarosis.     

Chronologic localization of mycoplasma hyopneumoniae in experimentally infected pigs

The chronologic localization of Mycoplasma hyopneumoniae was examined by in situ hybridization in experimentally infected pigs for a period of 35 days after intratracheal inoculation. M. hyopneumoniae DNA was detected in bronchial and bronchiolar epithelial cells from infected pigs at 7, 14, 21, and 28 days postinoculation (DPI) and in alveolar and interstitial macrophages and type I pneumocytes from infected pigs at 14, 21, 28, and 35 DPI. Strong hybridization signals for M. hyopneumoniae were detected mainly at the luminal surface of bronchial and bronchiolar lining epithelial cells. When a hybridization signal was detected at the luminal surface of bronchial and bronchiolar lining epithelial cells, a given bronchus or bronchiole also exhibited peribronchiolar lymphoid cuffing. These observations suggested that the presence of M. hyopneumoniae in different tissues could be due to a difference in the duration of the infection.     

Larval development of Toxocara canis in dogs

The parasitic roundworm Toxocara canis is present in dog populations all over the world. Due to its zoonotic potential, this roundworm is of special interest not only for veterinarians, but also for medical practitioners. In the present review, current knowledge of infection routes and the subsequent development of larvae within the canine host is summarised. Furthermore, information about the clinical, pathological, enzymatic, haematological and histopathological changes was collected, giving a broad overview of current knowledge of the infection. Although the data collected over the years give an idea of what happens during the larval development of T. canis, many questions remain open. Nevertheless, it is important that we continue our efforts to further understand the biology of this versatile and compelling parasite and try to improve and optimise strategies to prevent the infection in dogs and thereby to protect humans from this infection.     

Pathogenicity of Trypanosoma brucei brucei in experimentally infected pigs.

An experimental infection of 4-to 5-month old pigs with a stock of Trypanosoma brucei brucei resulted in a high parasitaemia, anorexia, pyrexia and a decline in the packed cell volume by one third. Nervous sign of circling and wobbling of the hind legs occurred in one of the pigs which at necropsy revealed a very severe meningo-encephalitis and the presence of trypanosomes in the brain. These results confirm that T. b. brucei might cause a severe disease in pigs.     

Toxocara canis: proteinases in perivitelline fluid from hatching eggs

Developing larvae of Toxocara canis may secrete several kinds of enzymes within the egg perivitelline fluid (EPF) prior to and during hatching. In particular, proteinases in EPF could play a role in larval emergence within the host gastrointestinal lumen but its presence and nature is unknown. In this work, proteolytic activities in hatching fluid of T. canis were identified and analysed by substrate gel electrophoresis at different pH values and by using type specific protease inhibitors. Three bands of 91, 68 and 38 kDa showed gelatinolytic activity and all proteinase activity from EPF was of the aspartic-type since it was inhibited by pepstatin A. Interestingly, a significantly higher proteolytic activity was observed at acidic pH (< or =5.5). These data suggest that T. canis developmentally secretes and accumulates in EPF aspartic proteinases with a pH-dependent activity that might help the parasite to take advantage of conditions in the host gastrointestinal microenvironment where egg hatching is induced and executed.     

Seroprevalence of Toxocara canis in sheep in Wales

Antibody levels to Toxocara canis L2 excretory/secretory antigens were examined by ELISA in 400 serum samples from sheep in Powys and Gwent, Wales. A positive OD value was set at the mean +/-3S.D. of 45 control samples. Seroprevalence increased with age. Seven percent and 13% of 6-month-old sheep showed positive OD values as did 16% of 10-month-old, 27% and 31% of 15-month-old and 47% of cull ewes. Analysis of variance showed a significant increase in ELISA OD values among the seropositive sheep with increasing age of sheep.     

Efficacy of selamectin against experimentally induced and naturally acquired ascarid (Toxocara canis and Toxascaris leonina) infections in dogs

The efficacy of selamectin against adult ascarids was evaluated in eight controlled and masked studies in dogs. Three laboratory studies evaluated selamectin against experimentally induced infections of Toxocara canis; three laboratory studies evaluated selamectin against naturally acquired infections of T. canis; one laboratory study evaluated selamectin against naturally acquired infections of both T. canis and Toxascaris leonina; one field study evaluated selamectin against naturally acquired infections of ascarids (T. canis and/or T. leonina) in dogs presented as veterinary patients. Selamectin was administered topically to the skin of dogs in unit doses designed to deliver a minimum of 6mgkg(-1) (range, 6-12mgkg(-1)). In all studies, dogs were allocated randomly to treatment assignments (selamectin or vehicle control in laboratory studies: selamectin or reference product in the field study) on the basis of pretreatment fecal egg counts. For induced infections, there were significant reductions in geometric mean numbers of adult T. canis after a single application of selamectin (93.9-98.1%, P=0.0001), after two monthly applications (> or =88.3%, P< or =0.0001), and after three monthly applications (100%, P< or =0.0002). In the natural infection laboratory studies, when selamectin was administered twice at an interval of 30 days, the percentage reductions in geometric mean numbers of adult T. canis at necropsy were 84.6, 91.3, and 97.9%, and when selamectin was administered on days 0, 14, and 30, the percentage reductions were 91.1 and 97.6%. Geometric mean fecal T. canis egg counts were reduced by > or =92.9% (P< or =0.0067) at the end of the studies. In the field study, geometric mean fecal ascarid egg counts were reduced by 89.5 and 95. 5% (P=0.0001) for 14 and 30 days, respectively, after a single treatment with selamectin, and by 94.0% (P=0.0001) 30 days after the second treatment with selamectin. These reductions compared favorably with the egg count reductions from dogs treated with a reference product containing praziquantel, pyrantel embonate, and febantel. There were no adverse drug experiences or treatment-related mortalities during any of the studies. Selamectin, when administered topically in a unit dose providing a minimum dosage of 6mgkg(-1), was safe and effective against adult T. canis and T. leonina and in reducing the fecal excretion of T. canis eggs in dogs.     

Acquired immunity to Toxocara canis infection in mice

Acquired immunity develops against Toxocara canis infection in mice, and NIH mice are more immunoresponsive than CD1 mice. Twice infected NIH female mice showed 27% reduction in the total larval recoveries compared with non-sensitized controls. Twice-infected NIH male, and CD1 (both sexes) mice showed a negligible reduction in the total recoveries, though a significant (P less than 0.05) number of larvae were retained in the liver compared with the non-sensitized controls. All twice-infected mice showed a significant reduction in the number of larvae recovered from the brain compared with once-infected mice. Vaccination using ultraviolet irradiated embryonated eggs gave the best protection against reinfection. Excretory/secretory antigen afforded less protection, whilst whole adult worm vaccine and whole L2 culture vaccine gave no protection. Vaccinated mice had a higher 'free:penetrating ratio' of larvae in their intestine than similarly challenged but non-vaccinated mice. When the ileum was examined histologically 9 h post-infection, an inflammatory reaction was seen around the penetrating larvae in the sensitized and vaccinated mice but not in untreated controls, suggesting a role played by the intestine in the resistance against T. canis infection in mice.     

The effect of free and polyethylene glycol-liposome-entrapped albendazole on larval mobility and number in Toxocara canis infected mice

As part of our exploratory drug research on the larva migrans that causes roundworm in dogs and cats, this study was carried out to clarify the effect of free and liposome-entrapped (LE) albendazole in Toxocara canis infected mice. In infected mice, evaluation of mobility and number of larva were examined in detail in the brain, skeletal muscle and liver. Larva mobility was evaluated by using the relative mobility (RM) value. Albendazole was LE as one of the drug delivery systems (DDSs). Polyethylene glycol (PEG) was added to the liposome in order to avoid evoking a response by the reticuloendothelial system (RES). By using the albendazole PEG-LE delivery system, it was possible to target the larvae in the mouse brain and liver resulting in a decrease in the number of larvae. In the skeletal muscle of the infected mice, the intraperitoneal dosages of PEG-LE albendazole did not cause a complete decrease in the number of larvae, even though free albendazole did cause the number to decrease. Therefore, it is necessary to take into consideration the migrating stage of the larvae before the initiation of any drug administration.     

Pharmacokinetics of ampicillin and sulfadimidine in pigs infected experimentally with Streptococcus suum

Twenty-three hybrid pigs (23 ± 3 kg body wt) were assigned to three groups to investigate the pharmacokinetics of ampicillin (APC, 10 mg/kg) administered intravenously (i.v.) and intramuscularly (i.m.), and sulfadimidine (SDM, 50 mg/kg) administered intravenously as a bolus injection. In the first series of experiments the animals remained healthy. Subsequently, the pigs were infected with Streptococcus suum by subcutaneous (s.c.) inoculation and the experiments were repeated. The total apparent distribution volume of APC given intravenously was increased from 0.512 ± 0.026 L/kg in uninfected pigs to 0.68 ± 0.06 L/kg (P < 0.01) in infected pigs, whereas there were no significant changes in the same parameter for SDM (P > 0.05). The clearance of APC was increased markedly from 0.52 ± 0.07 L/kg/h in uninfected pigs to 0.62 ± 0.10 L/kg/h in infected pigs. In contrast, SDM clearance was decreased markedly from 0.023 ± 0.003 L/kg/h to 0.017 ± 0.003 L/kg/h (P < 0.05). As a result, the biological half-lives of the drugs were altered to varying degrees in infected pigs. The half-life of SDM was increased from 15.0 ± 3.0 h in uninfected pigs to 20 ± 7h in infected pigs (P < 0.05), but differences in APC half-lives between uninfected and infected animals were not observed (P > 0.05). There were no statistically significant differences in pharmacokinetic parameters of APC administered by intramuscular injection between the healthy and the diseased status, although its half-life was shortened from 0.76 ± 0.22 h in the healthy to 0.57 ± 0.23 h in the diseased. The results suggest that blood concentrations of APC and SDM are affected differently by the same disease due to its specific effects on their distribution and elimination.     

Effects of ketoprofen and flunixin in pigs experimentally infected with Actinobacillus pleuropneumoniae

The antipyretic effect of the non-steroidal anti-inflammatory drugs (NSAIDs) ketoprofen (3 mg/kg) and flunixin (2 mg/kg) were studied in pigs. The drugs were administered intramuscularly at 8 and 32 h following endobronchial challenge with Actinobucillus pleuropneumoniae. Infected (non-medicated) and non-infected (non-medicated) controls were used. Endobronchial challenge with Actinobucillus pleuropneumoniae induced laboured breathing, coughing, fever, reduced food and water consumption and increased white blood cell counts. At autopsy, pleuropneumonia was evident. Ketoprofen showed a highly significant antipyretic effect but flunixin did not. The decrease in food consumption of ketoprofen-treated pigs was significantly less than that of the infected (non-medicated) controls. Blood parameters were not significantly influenced by either NSAID and, at necropsy, gastric and renal side-effects were not observed for either drug.     

Ocular lesions associated with Trypanosoma evansi in experimentally infected goats

Ocular lesions associated with Trypanosoma spp. infection have been described in man and many animal species. However, loss of vision has not been demonstrated in humans presenting Chagas disease or in animals affected by different trypanosome species. In order to assess the possible ocular disorders caused by Trypanosoma evansi infection, six goats were inoculated with 1 x 10(5) T. evansi and maintained for 12 months and four goats were used as control. The inoculated animals became positive at serological and parasitological tests at 1-month post-inoculation and showed a subclinical course of the disease. Unilateral superficial corneal ulceration and retinochoroiditis were observed in two inoculated animals. Data from ocular neurologic examination and electroretinography showed no significant differences between inoculated and non-inoculated goats. It could be concluded that Trypanosoma evansi can produce ocular lesion but without apparent loss of vision in goats.     

Systemic antibody response in colostrum-deprived pigs experimentally infected with Haemophilus parasuis

The serum antibody response to an experimental infection by Haemophilus parasuis, the etiological agent of Glässer’s disease in pigs, was characterized by ELISA measuring IgM and IgGt levels against whole-cells and outer-membrane-proteins (OMPs) as antigens. Five groups of pigs were studied, four of those were previously immunized with different formulations, and the fifth was maintained as non-immunized control. All groups were challenged with 5 × 10⁹ CFU of H. parasuis. The non-commercial bacterin induced a full protection against disease, the OMP-vaccine and the exposure to a sublethal dose of 10⁵ CFU protected only partially, and the recombinant TbpB-vaccine conferred no protection. The humoral response in the pigs that died after infection (all controls, all those vaccinated with the recombinant TbpB, and two of both those inoculated with OMPs and those exposed to the sublethal dose) could be only measured before it, but it was irrelevant in all cases. However, a specific IgM and IgGt production was observed before challenge in all the surviving pigs, irrespective of the type of immunization received. This antibody response was even greater after H. parasuis infection, especially in those survivors receiving the sublethal dose. These results suggest a role of the antibodies developed after the different immunization protocols in preventing infection and death; therefore, the humoral immunity is protective against experimental Glässer’s disease.     

Kinetics of circulating antigens in pigs experimentally infected with Taenia solium eggs

Three groups of four piglets were experimentally infected with different doses (10(3), 10(4) and 10(5)) of Taenia solium eggs whereas a fourth group of two pigs received gravid proglottids. At autopsy 6 months post infection, the two latter pigs were heavily infected with more than 3000 living cysts per kg of muscle. Ten of the 12 other pigs harboured light infections, i.e. between 2 and 107 cysticerci, 42.4% of which were degenerated. The two remaining pigs had no detectable cysts at post mortem examination. Circulating antigens (CA) were detected in the sera of all pigs harbouring living cysticerci using a monoclonal antibody based ELISA. CA were first detected between 2 and 6 weeks post infection and remained present generally throughout the entire observation period even in pigs carrying only five to eight living cysts, although strong fluctuations of the level of CA were observed in some pigs. In animals without living cysts at post mortem CA were only detected for a short period and disappeared presumably when the cysticerci became degenerated. The minimum number of living cysts, which could be detected using this ELISA, was 1.     

Growth performance and whole-body composition of pigs experimentally infected with Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae (Mh) is the primary infectious pathogen responsible for enzootic pneumonia in pigs. Although Mh is thought to impair growth performance, whole-body composition, and fat and protein accretion in pigs with pneumonia have not been reported and the mechanism through which Mh reduces growth is unknown. The objectives of this study were to evaluate the effects of Mh on growth performance, whole-body composition, and protein and fat accretion in nursery pigs and to determine whether Mh infection increases the expression of interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha). Sixty-four 2-wk-old Mh-free pigs were used (two trials) in a randomized complete block design. In each trial, two pigs were housed in each of 16 disease-containment chambers. At 4 wk of age, pigs were inoculated intratracheally with 3 mL of Mh broth (P5722-3, 10(7) cfu/mL) or sterile Friis culture medium. Clinical signs of disease and feed intake were monitored daily and body weight was determined weekly for 4 wk. Whole-body composition was determined from pigs killed 0, 14, and 28 d after inoculation, and the comparative slaughter technique was used to estimate protein and fat accretion. At death, gross lung lesions were quantified, and lung tissue was collected to verify the presence or absence of Mh, and to determine cytokine mRNA levels. Control pigs displayed no overt signs of infection and were Mh-negative and free of pulmonary lesions. Pigs inoculated with Mh showed pneumonic coughing (P < 0.005), were Mh-positive, and had pulmonary lesions that affected 4.5% (P < 0.01) and 14.1% (P < 0.001) of total lung surface area at 14 and 28 d, respectively, after inoculation. Ribonuclease protection assays revealed increased IL-1beta (P < 0.04) and TNF-alpha (P < 0.06) mRNA in lung tissue collected from a lesion site compared with tissue collected 10 cm from a lesion site or from control pigs. Interestingly, Mh did not depress weight gain or feed efficiency during any week of the 28-d study (P > 0.10). Moreover, Mh did not affect whole-body fat or protein accretion (P > 0.10). Thus, in spite of inducing disease and expression of inflammatory cytokines, Mh alone did not affect growth performance and whole-body composition of nursery pigs during the 4-wk experiment. The ability of pigs to contend with Mh may have resulted from the absence of other pathogens that generally co-exist with Mh under commercial conditions.     

Persistent activity of doramectin and ivermectin against Ascaris suum in experimentally infected pigs.

A study was conducted to investigate the persistent nematocidal activity of two avermectins against experimentally-induced infections of Ascaris suum in swine. Seventy-two nematode-free cross-bred pigs of similar bodyweight were randomly allotted to nine treatment groups of eight pigs each. Eight of the groups were treated with injectable solutions containing 300 microg of doramectin/kg (IM) or 300 microg of ivermectin/kg (SC) either 0 (same day), 7, 14, or 21 days prior to an oral challenge of 50000 embryonated A. suum eggs. The ninth group (control) was challenged in parallel without any avermectin treatment. At 41 or 42 days after challenge, pigs were euthanatized and adult and larval stages of A. suum were collected from the gastrointestinal tract of each pig and counted. Both avermectins significantly (P < 0.0002) reduced nematode counts when given on the day of challenge (0 days prior), and the efficacy was 100% and 97.5% for doramectin and ivermectin, respectively. Doramectin given 7 days prior to challenge significantly (P < 0.0001) reduced nematode counts, and the efficacy was 98.4%. For all other avermectin-treatment groups, nematode counts were not significantly reduced compared to those in control pigs. These data indicated that anthelmintic activity of ivermectin against A. suum persisted for less than 7 days and the activity of doramectin persisted for more than 7, but less than 14 days.