Treatment of pneumonia in pigs with long-acting injectable tylosin.

A blinded, randomised clinical trial was carried out in Brittany, France on three commercial pig farms with a history of pneumonia. Pigs with clinical signs of respiratory disease were randomly allocated to one of two treatment groups; 100 pigs received a single intramuscular injection of a long-acting formulation of tylosin at a dose rate of 20 mg tylosin/kg bodyweight, and 101 pigs received three consecutive daily intramuscular injections of 10 mg tylosin/kg bodyweight. The pigs' rectal temperatures and other clinical variables were recorded at intervals and a scoring system was used to evaluate the results of the treatments. Relapses were recorded for up to nine days after the treatment. There were no statistically significant differences between the two treatments in terms of clinical scores, rectal temperatures, or cure or relapse rates.

The effect of a parenteral ivermectin/closantel injection on the growth and reproductive development of early immature Fasciola hepatica in cattle.

Sixteen calves approximately 6 months old were each infected with 500 metacercariae of Fasciola hepatica. Thirty-two days later they were weighed and divided into two groups, and on day 35 all calves in one of the groups were injected subcutaneously with an ivermectin/closantel combination. Both groups were sacrificed between days 70 and 72 to enable counting and examination of the flukes recovered from the bile ducts. Eggs released by the flukes were collected for incubation, hatching and estimation of egg viability. Flukes were counted, flat-fixed in 70% ethanol, stained with catechol and carmine and measured. The reproductive organs, namely testis, vitelline glands, ovary and uterus, were examined and scored on a 0-3 scale according to their state of development. This was visually assessed on the basis of size, distribution and staining density of their constituent tissues and the abundance of eggs in the uterus. A representative sample of flukes from each animal was fixed in formalin for histological sectioning to enable more detailed examination of the reproductive structures. Treatment of the immature flukes reduced the population in cattle by 42.6% as compared with the controls and as a result of the stunting effect due to the presence of closantel during early development the size of treated flukes was reduced by 43.9%. A bimodal pattern of size and reproductive score was also observed in flukes from treated cattle, suggesting that the stunting effect on individual flukes differed depending on whether or not they had gained access to the bile ducts or were still migrating in the hepatic parenchymal tissue at the time of drug exposure with the effect being greater once the fluke had gained access to the bile ducts. The mean reproductive score for untreated flukes was 8.76 and for treated flukes 5.64, a 35.6% reduction. This difference was highly significant (p<0.001). Egg shedding from treated flukes was significantly less than that from controls (p<0.05), but there were no differences in hatchability, suggesting that whilst drug treatment reduced the energy supply available for gametogenesis/oogenesis, it did not induce functional defects in the gonads or accessory reproductive organs. Histological examination confirmed that there was a reduction in development of testes, ovaries and vitellaria in treated flukes, with a consequent reduction in egg production. In the treated flukes, early spermatogonia and oogonia were the predominant cell types in the testes and ovary, whilst undifferentiated stem cells were abundant in the vitelline follicles. In untreated flukes, cells representing more advanced stages in gametogenesis and vitellogenesis predominated in the respective organs. It is likely that this inhibition of gametogenesis and vitellogenesis was caused by the effects of closantel treatment on intermediary metabolism in the flukes. Clearly these effects were evident even at a relatively early stage of fluke growth, and because of the impact on egg output may have epidemiological importance in addition to the reduction in fluke numbers.

Pharmacokinetics of a novel closantel/ivermectin injection in cattle.

Two studies are described on the pharmacokinetics of a combination anthelmintic consisting of ivermectin and closantel for use in cattle. In the first, the pharmacokinetics of both active drugs in the combination were compared with the formulation with either ivermectin or closantel removed. No differences in the pharmacokinetics were observed, indicating that neither the absorption nor distribution of ivermectin or closantel in the combination were influenced by the presence of the other. In the second study the pharmacokinetics of ivermectin and closantel in the combination product were compared with control formulations of each. No difference was found between the closantel formulations. With ivermectin it was noted that absorption and excretion were more rapid and Cmax higher in the combination, although the AUC of both formulations were not significantly different.

Vertical transmission of hepatitis C virus in New Zealand.

AIMS: To investigate the transmission of hepatitis C virus from viraemic mothers to infants. METHODS: The study group comprised 54 hepatitis C ribonucleic acid (RNA) positive, human immunodeficiency virus (HIV) negative women attending antenatal clinic, their infants when born, 12 previous children and 44 children of 29 additional nonpregnant, viraemic women. During the study period there were 60 live births (1 set of twins, 5 sequential pregnancies). All infants were tested at birth for hepatitis C virus (HCV) RNA. Thirty infants were retested at 6 months or later. Breast milk from 30 mothers was tested for HCV RNA. The 56 other children were tested for antibody to HCV and HCV RNA. RESULTS: Of the 60 infants tested at birth, 30 failed to attend a 6 month or later followup, 2 infants were HCV viraemic by six months of age, 2 infants had one episode of possible HCV RNA positivity followed by loss of detectable HCV RNA and 26 have shown no evidence of HCV infection. Five of the 30 breast milk samples tested were positive for HCV RNA. Four older children of viraemic mothers were HCV RNA positive. CONCLUSIONS: In this study, 2 of 30 (6.6%) of infants born to HIV negative, HCV viraemic mothers acquired HCV infection. Breast milk remains a possible contributory source of infant HCV infection. Management of babies born to HCV viraemic mothers should include retesting of baby for HCV RNA at 3 to 6 months of age.

Hepatitis C virus seroprevalence in patients attending a sexual health centre.

AIM: To determine the prevalence of hepatitis C virus (HCV) infection in patients attending the Christchurch sexual health centre. METHODS: Anonymised unlinked serum specimens from 362 patients sequentially attending the sexual health centre were obtained and tested for HCV antibody using the second generation enzyme immunoassay kit (Abbott). Antibody positive samples were assayed for virus by amplification of hepatitis C ribonucleic acid (RNA). RESULTS: Twelve patients (3.3%) were seropositive and 10 samples were also positive for virus RNA (2.7%). In 50% of cases the patients had no discernible risk factors other than unprotected sexual intercourse. An overall serum prevalence of 22% (4/19) was noted within a sub population who admitted to intravenous drug use. Ninety patients had, at the time of consultation, requested an antibody test for the human immunodeficiency virus (HIV). There were no antibodies to HIV detected in any of these patients nor any statistical difference in HCV antibody prevalence within this group. CONCLUSION: Hepatitis C is a common viral infection within the community. A significant percentage of patients who were anti HCV positive had no discernible risk factors other than sexual transmission which must be considered as a mode of transmission. We concur with the Department of Health guidelines emphasising the need for safer sex practices in a patient with a diagnosis of hepatitis C.

An unusual strain of hepatitis C virus in New Zealand.

AIMS: To investigate the prevalence of hepatitis C virus (HCV) viraemia in selected cohorts of New Zealand patients and to examine the strains of hepatitis C virus circulating in New Zealand. METHODS: Hepatitis C viraemia was identified using a highly sensitive polymerase chain reaction (PCR) assay to detect HCV ribonucleic acid (RNA). Selected virus isolates were analysed for strain variation by restriction fragment length polymorphism (RFLP) of PCR products and two of the amplified products were sequenced. RESULTS: A high frequency of HCV viraemia was found in patients with a history of repeated exposures to blood or blood products. RFLP analysis revealed the prevalence of an unusual strain of hepatitis C which was further confirmed by sequencing. Identification of the infecting hepatitis C strains resolved a suspected point source outbreak occurring in a maximum security prison. CONCLUSIONS: Detection of circulating hepatitis C RNA is a sensitive and specific method for identifying active hepatitis C infection. Typing hepatitis C isolates has useful epidemiological application and facilitates the detection of unusual HCV variants.

T cell receptor alpha-chain polymorphic allele frequencies in Caucasians and Polynesians.

Restriction length polymorphisms in the variable and constant regions of the T cell receptor alpha-chain were examined in 42 Caucasians, 29 Maoris and 27 Pacific Islanders. Southern blots of Taq I digested DNA were hybridized with the T cell receptor alpha-chain probe pY14. Our results confirm that a 1.4 kb T cell receptor alpha chain-Taq 1 band is allelic to a 0.5 kb band. A significant difference in the frequency of the 1.4 and 0.5 kb alleles of the variable region of the alpha-chain was detected in Caucasians when compared with Maoris or Pacific Islanders (P < 0.0001). No differences in the frequency of the 2.0 and 7.0 kb alleles of the constant region gene were detected between any of the racial groups. These data may be relevant to ethnic differences in susceptibility to immune disorders.