Effect of chronic trypanosomiasis on immunization against East Coast fever

Two experiments were carried out in which uninfected cattle, or cattle chronically infected with Trypanosoma congolense, were immunized by the infection and treatment method against East Coast fever (ECF; Theileria parva infection). Chronic trypanosomiasis did not prevent cattle mounting an effective immunological response to ECF immunization and resisting subsequent lethal challenge. There appeared to be no difference in the level or quality of immunity between uninfected cattle and trypanosome-infected cattle. Thus, T. congolense infection on its own does not appear to provide a constraint to ECF immunization in the field.     

Influence of dietary protein supply on resistance to experimental infections with Haemonchus contortus in Ile de France and Santa Ines lambs

The effect of Haemonchus contortus infection in sheep fed with a moderate and high protein content diet was evaluated in two breeds of sheep. Forty-eight Ile de France and Santa Ines lambs were maintained indoors since birth, in worm-free conditions. The lambs were allocated after weaning in four groups of six animals per breed, which were either infected or remain uninfected and given access to either a moderately or highly metabolizable protein diet. The moderately and highly metabolizable protein diets were calculated to supply 75 and 129 g metabolizable protein per kg of dry matter (MP/kg DM), respectively. The infection consisted of a trickle infection with 300 infective larvae, three times a week, for 12 weeks. Significant differences were observed for mast cell, globule leukocyte and eosinophil counts in the abomasal mucosa of the infected groups compared to the control of both breeds (P<0.05), regardless of the diet supplied. Significantly higher IgA anti-L5 antibody was detected in the infected Santa Ines groups than in the infected Ile de France groups (P<0.05). Increased metabolizable protein supply resulted in larger body weight gain and higher packed cell volumes for both breeds (P<0.05). Both breeds showed an increased ability to withstand the pathophysiological effects of H. contortus infection when given access to the highly metabolizable protein diet. However, increased metabolizable protein supply resulted in reduced worm burdens in Santa Ines lambs but not in the Ile de France lambs (P<0.05). The present results show that the increase in protein content in growing lamb diets may benefit resistance and resilience to gastrointestinal parasites but that these benefits may vary among breeds.     

Suppression of immune response to sheep red blood cells in rats experimentally infected with

A direct haemagglutination assay for antibodies to sheep red blood cells (SRBC) was used to assess the response of rats infected with Trypanosoma brucei gambiense. Whereas uninfected rats showed an efficient primary and secondary immune response to SRBC, trypanosome-infected rats displayed depressed antibody response starting about six days after infection. Infected rats failed to respond to a challenge dose of SRBC given 14 days after infection while uninfected control animals responded with an increased level of antibody production. These observations showed that T. b. gambiense infection inhibited both primary and secondary immune response to SRBC in rats. The result of this experiment is very important with regard to serological methods used to detect increasing levels of antibody production for diagnosis of diseases caused by bacterial and viral pathogens. In a concurrent trypanosome infection such increasing antibody levels would not be observed, leading to inaccurate diagnosis. Thus trypanosomiasis infection should be excluded under field conditions before the value of a serological diagnosis can be fully utilized.     

Suppression of immune response to sheep red blood cells in rats experimentally infected with Trypanosoma brucei gambiense

A direct haemagglutination assay for antibodies to sheep red blood cells (SRBC) was used to assess the response of rats infected with Trypanosoma brucei gambiense. Whereas uninfected rats showed an efficient primary and secondary immune response to SRBC, trypanosome-infected rats displayed depressed antibody response starting about six days after infection. Infected rats failed to respond to a challenge dose of SRBC given 14 days after infection while uninfected control animals responded with an increased level of antibody production. These observations showed that T. b. gambiense infection inhibited both primary and secondary immune response to SRBC in rats. The result of this experiment is very important with regard to serological methods used to detect increasing levels of antibody production for diagnosis of diseases caused by bacterial and viral pathogens. In a concurrent trypanosome infection such increasing antibody levels would not be observed, leading to inaccurate diagnosis. Thus trypanosomiasis infection should be excluded under field conditions before the value of a serological diagnosis can be fully utilized.     

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.     

Trypanosome-induced hypothyroidism in cattle.

Three Boran (Bos indicus) cattle infected with T. congolense IL 1180, and two uninfected control Boran cattle were used to study the effect of trypanosomiasis on the function of the thyroid gland. On a weekly basis, plasma thyroxine (T4) was measured by 125I-radioimmunoassay. Results indicated that T. congolense caused a significant decline in plasma T4 concentration in infected animals.     

Thrombocytopenia and platelet activity in dogs experimentally infected with Rangelia vitalii

The aim of this study was to evaluate the platelet count, coagulation time and platelet activity in dogs experimentally infected with Rangelia vitalii during the acute phase of the disease. For this study, 12 young dogs (females) were used, separated in two groups. Group A (uninfected control) was composed by healthy dogs (n=5), and group B consisted of R. vitalii-infected animals (n=7). After being inoculated with R. vitalii-infected blood, animals were monitored by blood smear examinations, which showed intra-erythrocytic forms of the parasite five days post-inoculation (PI). Blood samples were collected on days 0, 10, 20 and 30 PI. The material collected was placed in tubes containing EDTA for quantification of platelets, citrate anticoagulant platelet aggregation, and measuring the clotting time. Right after blood collection on days 10 and 20 PI, dogs were anesthetized for collecting bone marrow samples. A significant reduction (P<0.01) of the number of platelets was observed in R. vitalii-infected blood, when compared with uninfected dogs on days 10 and 20 PI. Additionally, macro-platelets were observed only in infected dogs. Prothrombin time and activated partial thromboplastin time did not differ between infected and uninfected dogs. The megakaryocyte count increased (P<0.01) significantly in infected dogs when compared with uninfected ones on days 10 and 20 PI. Platelet aggregation decreased (P<0.01) significantly in infected dogs in comparison to the control on days 10 and 20 PI. Therefore, rangeliosis in dogs causes a severe thrombocytopenia during the acute phase of infection. This platelets reduction probably occurred due to splenic sequestration and/or immune-mediated thrombocytopenia.     

Effects of Fasciola gigantica infection on growth and nutrient utilisation of buffalo calves

The effects of Fasciola gigantica infection on bodyweight gain, dry matter intake, digestibility of nutrients and feed conversion efficiency in buffalo calves were investigated. Nine male buffalo calves of the Murrah breed, aged 12 to 15 months with a mean (se) bodyweight of 166 (12.5) kg, were randomly assigned to groups of five (group 1) and four (group 2). The animals in group 1 were given 1000 viable, mature metacercariae of F gigantica orally, while the animals in group 2 served as uninfected controls. They were stall fed on diets containing a concentrate mixture and ad libitum wheat straw and were maintained by standard management practices for a period of 165 days after infection. The average daily liveweight gain of the infected animals was 110.6 g, compared with 439.4 g in the uninfected controls, and was associated with the appearance and establishment of immature flukes in hepatic bile ducts. The feed conversion efficiency declined significantly (P<0.01) from 41 days after infection and was lowest at the end of the experiment. F gigantica infection did not influence the digestibility of the nutrients. The impaired feed conversion efficiency was mainly due to a reduction in dry matter intake due to inappetence.     

Hypothalamic-pituitary-adrenal axis responsiveness to insulin-induced hypoglycaemia is modified by trypanosome infection in Boran (Bos indicus) cattle.

Ten Boran (Bos indicus) cattle were used to study the stress responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis during trypanosome infection. Five cattle were infected with Trypanosoma congolense IL 1180 by tsetse challenge and five cattle served as controls. All infected animals developed acute trypanosomiasis. Insulin-induced hypoglycaemia (50 per cent of pre-insulin glucose concentration) was used as a stress factor. Acute hypoglycaemia was observed in three infected and three control animals after insulin challenge. Two animals from each group either did not respond or responded slowly. Hypoglycaemia in infected animals completely failed to induce an HPA axis response, while in control animals an HPA axis response was indicated by a significant increase in plasma adrenocorticotrophic hormone (ACTH) and cortisol concentrations (P less than 0.01). The results show that trypanosomiasis in Boran cattle can cause a decrease in the stress responsiveness of the HPA axis as indicated by a blunted ACTH/cortisol response to insulin-induced hypoglycaemia.     

Plasma lipopolysaccharide elevations in cattle associated with early-stage infection by Fasciola hepatica

Fasciolosis is an endemic zoonotic parasitic disease with significant impacts on human health and both animal health and production. Early post-infection impacts on the host remain unclear. The objective of this study was to determine the changes, if any, to levels of endotoxin in cattle plasma in response to early-stage infection with Fasciola hepatica. Thirty-six (36) commercial bred cattle were experimentally infected with approximately 400 viable metacercariae. Plasma lipopolysaccharide (endotoxin) levels were examined on 24 occasions from 0 h before infection to 336 h after infection using the Limulus Amoebocyte Lysate chromogenic end point assay and compared with that of six (6) uninfected control animals. Peak lipopolysaccharide levels in infected animals were reached at 52 h after infection and returned to pre-infection levels at time 144 h after infection. Infected animals had significantly elevated lipopolysaccharide levels between 24 and 120 h after infection when compared to uninfected animals. The mean change in endotoxin units (EU)/mL over time after infection was statistically significant in infected animals. Elevations of lipopolysaccharide occurred in all infected animals suggesting a possible repeatable and titratable endotoxemia conducive to therapeutic agent model development.     

The influence of dietary protein on live bodyweight, degree of anaemia and erythropoietic responses of Scottish Blackface sheep infected experimentally with Trypanosoma congolense

The present study investigated the influence of dietary protein on the intensity of parasitaentia, degree of anaemia and erythropoietic responses, in sheep experimentally infected with Trypanosoma congolense and given either a high protein diet (116 g digestible crude protein [dcp] per day) or a low protein diet (51·5 g dcp per day). It was observed that infected and control animals on the high protein diet grew at similar rates while infected animals on the low protein diet experienced marked retardation of growth compared with their uninfected controls. Dietary protein had no influence on the degree of anaemia that followed infection. Measurement of blood volumes revealed that low protein infected group had significantly lower mean circulating red cell volume than their controls. Ferrokinetic measurements indicated that plasma iron turnover rates (pitr) and ⁵⁹Fe incorporation rates were higher in the high protein infected group than in the low protein infected group, although these differences were not significant. These observations indicate that infected animals on a high protein tended to show greater enhancement of erythropoietic activity that infected animals on low protein diet.     

Trypanosomiasis challenge estimation using the diminazene aceturate (Berenil) index in Zebu in Gabon

A longitudinal study was conducted within a cattle ranch in Gabon to determine the diminazene aceturate (Berenil) index (DAI) in a group of Zebu, raised under low tsetse density; this measure providing an assessment of trypanosomiasis risk. The objective was to evaluate the trypanosomiasis pressure thus informing trypanosomiasis control methods and cattle management. Twenty female adult Zebu were monitored for 24 weeks during the dry season. Blood samples were collected on a weekly basis and subjected to parasitological and haematological analysis (n?=?480), using the buffy-coat method and the packed cell volume value (PCV), respectively, infected animals were treated with a single intramuscular injection of diminazene aceturate (8 mg/kg). Twenty-nine single infectious events were recorded and a DAI of 1.45 was calculated. Two trypanosome species were identified: Trypanosoma congolense (96.2%) and Trypanosoma vivax (3.8%). The mean PCV value of the infected animals was lower (26.6) compared to non-infected animals (32.0). This study shows that DAI may be a useful tool to assess trypanosomiasis. However, this is a time-consuming method that may be improved by using randomly selected sentinel animals to adapt the chemoprophylactic schemes, hence decreasing the costs and the drug resistance risk.

     

Primary experimental infection of riverine buffaloes with Fasciola gigantica.

The clinical course of the primary experimental Fasciola gigantica infection was investigated in riverine buffalo calves of the Murrah breed. Nine male calves aged 12-15 months were randomly assigned to two groups of five (Group I) and four (Group II) animals. Each animal in Group I, was orally infected with 1000 metacercariae (mc) of F. gigantica, whereas Group II animals did not receive any infection dose and served as uninfected controls. No clinical signs of fasciolosis were observed until the sixth week post-infection (PI). Group I animals, however, developed recognised symptoms of acute fasciolosis, comprising apyrexic inappetance, anemia, poor weight gain, diarrhoea and sub-mandibular and facial oedema, respectively, from 5, 6, 8, 16 and 17 weeks PI. The signs were intermittent in nature and of variable duration. The prepatent period was of 92-97 days (mean 95.2 +/- 3.1). One of the five infected animals died on Day 147 PI. At necropsy, 36.8 +/- 11.0% of the infection dose was recovered as adult fluke population. The gross lesions were primarily biliary in nature. Group II, the uninfected controls, throughout the study period of 165 days PI, did not show any symptom and were negative for F. gigantica. The study demonstrated that the onset of adverse effects of F. gigantica on the growth and health of the infected host was mainly noted during late prepatency much before coprological prediction and diagnosis. The significance of preventive therapy against fasciolosis during prepatency has been stressed in endemic areas.     

The serum glucose and beta-hydroxybutyrate levels in sheep with experimental Fasciola hepatica and Fasciola gigantica infection

The influence of Fasciola hepatica and Fasciola gigantica infection on serum glucose and beta-hydroxybutyrate (beta-HOB) in sheep was evaluated. This was done by setting up two groups of sheep. The first group (n=13) was split in two sub-groups, one experimentally infected with F. hepatica (n=9) and the other (n=4) as uninfected control. A second group consisting of a sub-group experimentally infected with F. gigantica (n=9) the other sub-group (n=6) left as uninfected control was also set up. The results of weight gain, parasitological and serum liver enzymes activity (glutamate dehydrogenase [GLDH] and gamma glutamyltransferase [gamma-GT]) used in monitoring the infection showed that all infected animals developed fasciolosis. It was observed that a reduction in serum glucose levels was significantly lower (p<0.05) in F. hepatica infected sheep than in uninfected control sheep starting from 5 weeks post-infection (wpi) to the end of the experiment. Similar reduction was recorded in F. gigantica infected sheep between 8 and 19 wpi. In contrast, serum beta-HOB levels were elevated in F. hepatica infected sheep between 6 and 16 wpi and in F. gigantica infected sheep between 7 and 15 wpi. It would appear from these serum glucose and beta-HOB levels that fasciolosis does lead to energy deficiency (low glucose) and ketosis (increased beta-HOB). The decrease in serum glucose and increase in serum beta-HOB levels in infected sheep may help in understanding the interaction between fasciolosis and nutritional status of infected ruminants especially in young growing animals.     

Neurological trypanosomiasis in quinapyramine sulfate-treated horses—a breach of the blood–brain barrier?

Trypanosoma evansi infection typically produces wasting disease, but it can also develop into a neurological or meningoencephalitis form in equids. Trypanosomiasis in horses was treated with quinapyramine sulfate, and all the 14 infected animals were recovered clinically. After clinical recovery, four animals developed a neurological form of the disease at various intervals. Two of these animals treated with diminazene aceturate recovered temporarily. Repeated attempts failed to find the parasite in the blood or the cerebrospinal fluid (CSF), but all of the animals were positive in enzyme-linked immunosorbent assay. The calculation of the antibody index (AI) in the serum and the CSF and polymerase chain reaction (PCR) analysis of the CSF and brain tissue were carried out to confirm the neuro-infection. We found PCR and AI analyses of the CSF to be useful tools in the diagnosis of the neurological form of trypanosomiasis when the organism cannot be found in the blood or CSF. The increased albumin quotient is indicative of barrier leakage due to neuroinflammation. The biochemical changes in the CSF due to nervous system trypanosomiasis include increases in the albumin quotient, total protein, and urea nitrogen. It seems to be the first report on relapse of the nervous form of trypanosomiasis in equids even after quinapyramine treatment in endemic areas.     

Efficacy of in-feed medication with tylosin for the treatment and control of Mycoplasma hyopneumoniae infections

The efficacy of in-feed medication with tylosin for the treatment of enzootic pneumonia was examined in an experimental Mycoplasma hyopneumoniae infection model. One group of 10 conventional M. hyopneumoniae-free pigs was inoculated intratracheally with a highly virulent field isolate of M. hyopneumoniae; a second group of 10 pigs was inoculated in the same way and after 12 days was given tylosin at 100 mg/kg feed for 21 days; a third group of 10 pigs was inoculated with sterile culture medium, and these pigs were not given tylosin. The pigs were examined daily for clinical signs and each pig was given a respiratory disease score. Thirty-three days after they had been infected the pigs were euthanased, the lung lesions were quantified and samples of lung were processed for immunofluorescence testing for M. hyopneumoniae. The mean (sd) respiratory disease and lung lesion scores were significantly higher (P<0.05) in both the infected groups than in the uninfected group. Between 23 and 33 days after infection the mean respiratory disease score of the pigs treated with tylosin was 0.54 (0.22), significantly (P<0.05) lower than that of the infected pigs which were left untreated, 1.54 (0.46); similarly, their average lung lesion score, 1.72 (1.20), was significantly lower than that of the untreated pigs, 5.27 (3.85).     

Florfenicol feed supplemented decrease the clinical effects of Mycoplasma hyopneumoniae experimental infection in swine in México

The therapeutic value of Florfenicol feed supplemented was evaluated in conventional pigs to eliminate consequences of chronic infection of Mycoplasma hyopneumoniae. The experimental animals were pigs with an average of 16 kg, after intratracheally inoculation with M. hyopneumoniae they were divided in two experimental groups: (a) the non-medicated; and (b) the feed supplemented group (20 g Florfenicol/ton of feed) during the ensuing 35 days. The average daily weight gain of the Florfenicol-treated pigs (0.33±0.14 kg/day) was significantly higher than that of the non-treated ones (0.21±0.10 kg/day). In medicated animals was still impaired relative to that of the uninfected ones control group (0.39±0.02 kg/day). The average percentage of pneumonic gross lesions extensions' of the pigs groups was: 13.99% for M. hyopneumoniae infected non-medicated group; 1.79% M. hyopneumoniae infected, Florfenicol-treated group and, 0.56% of the uninfected control group. M. hyopneumoniae; colonization was detected at these levels in 7 and 9 members of the respective infected groups. The extent of the pneumonic lesions and M. hyopneumoniae generally was greater in the non-medicated pigs. Therefore, oral administration of Florfenicol via feed ingestion seemed to be somewhat effective in ameliorating the clinical effects of M. hyopneumoniae infection of swine.     

Partial purification of somatic and excretory-secretory products of adult Fasciola hepatica and their application for the serodiagnosis of experimental and natural fascioliasis using an ELISA

Six partially purified antigen fractions from adult Fasciola hepatica (three somatic tissues [Fhs] and three excretory products [Fhm]) were used in a micro-ELISA to monitor the serum antibody levels of an experimental rabbit F hepatica infection. Fhs 1 detected infection after 19 to 26 days and the titre remained significantly higher than that of the controls until day 103 of infection (end of experiment). Using Fhm 1 and Fhm 2, antibodies were detected between 12 and 19 days after infection. Fhm 2 distinguished infected from uninfected rabbits during the entire experimental period, whereas Fhm 1 did not. Excretory-secretory products of a low molecular weight were also antigenic and could differentiate between infected animals and controls. One hundred and nine sera from naturally infected cattle and uninfected controls were tested with the same antigens. Although antibody was detected, the results were inconsistent and further purification of the antigens may eventually improve the sensitivity of the method.     

Effects of Practices Related to Catch-and-Release Angling on Mortality and Viral Transmission in Juvenile Largemouth Bass Infected with Largemouth Bass Virus

Abstract

Largemouth bass virus (LMBV; family Iridoviridae) has recently emerged as a causative agent in fish kills of largemouth bass Micropterus salmoides. Little is known about how the virus is transmitted or what factors predispose fish to mortality subsequent to infection. Concern has nevertheless arisen that activities related to recreational angling may affect transmission dynamics and may alter the susceptibility of infected fish to clinical disease. This study examined the separate effects of two angling-related factors on the susceptibility of juvenile largemouth bass to mortality from LMBV infection and on the transmission of LMBV from infected to uninfected fish. The first factor was hook-and-line angling. Infected fish that underwent a simulated angling treatment did not experience higher mortality or have higher viral loads in their tissues than those that were not angled. The second factor was direct contact between infected and uninfected fish, as would occur in live wells and holding tanks. The LMBV was transmitted from infected to uninfected fish through water, even when direct contact was prevented. Transmission of LMBV between infected and uninfected fish separated by a fenestrated barrier was nearly as efficient as LMBV transmission between infected and uninfected fish that were allowed direct contact. These results imply that angling itself may have only minimal effects on the survival of largemouth bass infected with LMBV but that angling-related practices that place infected and uninfected fish together in a limited water volume may facilitate viral transmission. Partitioning or cooling of live wells and holding tanks, as well as limiting their use, could reduce LMBV-associated mortality and viral transmission.     

Dehydroepiandrosterone increases resistance to experimental infection by Trypanosoma cruzi

Dehydroepiandrosterone (DHEA) enhances immune responses against a wide range of viral, bacterial, and parasitic pathogens. In a previous study, we reported that administration of DHEA significantly decreased the numbers of blood parasites in Trypanosoma cruzi experimental infection. The present study was undertaken to determine the effectiveness of DHEA in reducing the severity of acute phase T. cruzi infection of male and female Wistar rats. Animals were treated subcutaneously with 40 mg/kg body weight/day of DHEA. The concentration of nitric oxide (NO) was determined in spleen peritoneal cavity. Interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) were determined in the sera of uninfected and infected animals. DHEA treatment augments NO production for both sexes after in vitro LPS treatment for uninfected animals. Infection triggered enhanced NO levels although not significant. IL-2 and IFN-gamma were detectable in higher concentrations in treated and infected rats of both genders when compared to untreated controls. These data suggest that DHEA may have a potent immunoregulatory function that can affect the course of T. cruzi infection.