Drug resistance in pathogenic African trypanosomes: what hopes for the future?

Trypanosomosis is a serious threat to both man and animals mostly in Africa. Although the first pathogenic trypanosome was discovered over a hundred years ago, there is still no prospect for effective control or eradication of the disease through the development and use of vaccines because of the phenomenon of antigenic variation. Control continues to rely heavily on chemotherapy and vector control strategies. This therapy and prophylaxis depends on the use of drugs which, apart from having been developed over 5 decades ago, suffer from such limitations as toxicity and with their continued use, drug resistance. Resistance to currently used drugs is a serious problem in most fields of anti-microbial chemotherapy, particularly in the case of trypanosomosis where resistance and cross-resistance in animals and man have been developing rapidly. The frequently and widely reported decreasing efficiency of available trypanocides, difficulties of sustaining tsetse control and little hope that a conventional, anti-trypanosome vaccine will be produced in the near future, increase the imperative need for new drugs and alternative effective ways for the control of trypanosomosis. This review examines aspects of drug resistance in pathogenic trypanosomes, measures to minimise it, areas of future research in new drug targets and alternative control strategies. Based on these, it is our opinion that for now the management and control of trypanosomosis will continue to depend on proper usage of the few available trypanocides, especially strategic deployment of the sanative drugs in order to reduce the development of drug resistance, in addition to the continued use of environmentally friendly vector control programmes such tsetse trapping.     

The human-canine environment: a risk factor for non-play bites?

Few dog bite risk factor studies have been conducted. This veterinary clinic-based retrospective cohort study was aimed at identifying human-canine environmental risk factors for non-play bites in Kingston, Jamaica (660) and San Francisco (SF), USA (452). Data were analysed using modified Poisson regression with confounders selected using directed acyclic graphs (DAGs) and the change-in-estimate procedure. Dogs acquired for companionship were more likely (RR=1.66; 95% CI 1.02-2.70) to bite than those acquired for protection. Routinely allowing a dog into the presence of visitors was also positively associated with it biting. A dog sleeping in a family member's bedroom was a risk factor for biting in Kingston (RR=2.54; 95% CI 1.43-4.54) but not in SF, while being able to leave the yard unaccompanied was a risk factor for biting in SF (RR=3.40; 95% CI 1.98-5.85) but not in Kingston. Overall, dogs which were less restricted in their interactions with humans were at elevated risk for biting. An observed association with dog bites in one cultural setting might not exist in another.     

Are probiotics useful for therapy of Helicobacter pylori diseases?

Chronic infection with Helicobacter pylori (H. pylori) is a known risk factor for gastric cancer. Eradication rate of H. pylori infection by the classic triple treatment of PPIs and antibiotics is low. Therefore, probiotics are a useful tool for improving the rate of eradication and reduction of side effects. Several studies in animal models showed that Lactobacillus spp. alone and in combination with other probiotic strains have inhibitory effects on growth and suppression of inflammatory responses in H. pylori infections. However, some studies showed significant effects of Pediococcus strains on suppression, survival, and eradication of H. pylori infections. Therefore, it is suggested that in the treatment of H. pylori infections along with the usual probiotic strains, different strains of Pediococcus could be used. Recent studies showed that Lactobacillus reuteri and Lactobacillus gasseri alone with PPIs in human have a high eradication effect on H. pylori infections and it is suggested as the probiotic treatment of patient's in future therapeutic protocols. In relation to the probiotic treatment process, it should not be recommended that probiotics could be used as a single treatment for H. pylori eradication. However, use of probiotics as a supplement will increase eradication and reduce side effects associated with treatment. It is widely believed that probiotics could improve the eradication of H. pylori and reduce side effects during standard treatment, but some probiotic bacterial species could be useful with drug therapy. Generally, probiotic supplements could increase the eradication rate of H. pylori infections and reduced the side effects of antibiotics.     

Partition of sire effects for international sire evaluation in the presence of genotype×environment interaction

Both simulation and field data were analyzed to compare the current MACE (multiple-trait across-country evaluation) and a proposed partition model (MACE_P) for international sire evaluation in the presence of genotype–environment (GE) interaction. The partition model decomposes the sire effect into two components: constant effect that is stable genetically across countries and interaction effect that varies from country to country. Simulation results indicate that interaction effect was estimated more accurately by MACE_P when GE interaction is strong than when it is weak. The accuracy of estimating sire effects increased as GE interaction and/or heterogeneity of sire variances between countries lessened, indicating the importance of accounting for GE interaction and heterogeneous sire variances in the international genetic evaluation. A joint analysis of Japanese and the US Holstein populations reveals that the estimated interaction correlation (r_I) as a new measure of GE interaction was 0.924, suggesting little evidence of sire by country interaction for milk yield. A general formula was developed to convert the estimates of sire effects from MACE to MACE_P. Although MACE_P demands more computing resources than MACE, the use of this simple conversion formula would greatly reduce the computing requirements by MACE_P. Both constant and interaction effects estimated by MACE_P sums to the sire effect estimated by MACE. Sire (co)variances obtained as a sum of constant and interaction (co)variances estimated by MACE_P were very similar to those estimated by MACE. The partition of sire effect into the constant and interaction effects by MACE_P allows the indexing of these two component traits with different weights to maximize overall response in the presence of GE interaction.     

Intensive housing: the last straw for pigs?

The concept of coping can be used to relate the environmental conditions provided for livestock to their responses--their productivity and their welfare. Pigs are "ecological generalists" and hence are "designed" to cope with a wide variety of environmental conditions. They, however, show clear limits to their adaptability both in terms of the space they require and the pen materials they can endure without injury. Even where they adapt to a wide range of conditions, there often is a particular environment that gives optimum performance. Examples of temperature requirements and feeding facilities are discussed. The process of coping is shown to impose a biological "cost" in some instances and, although a pig has adapted to a specific environment, questions still remain concerning whether keeping a pig in that environment is justifiable.