Single-clone and mixed-clone infections versus host environment in Crithidia bombi infecting bumblebees.

Current theories assume that adaptive parasite evolution explains variation in the level of virulence and parasite success. In particular, mixed-genotype infections by parasites should generally be more virulent, and faster multiplying strains more successful, either because fixed strategies have evolved or because parasites facultatively alter virulence in response to co-infecting competitors. We compared several measures of parasite success and virulence between single-clone and mixed-clone infections of 2 strains of the trypanosome Crithidia bombi in its bumblebee host, Bombus terrestris. Contrary to expectation, we could not find differences between single-clone and mixed-clone infections in parasite prevalence, infection success, duration and clearance rate. However, a clearly significant effect of colony on infection intensity was present, and the colony effect emerged in virtually all other measures. We thus conclude that host environment as defined by the family (colony) genotype and thus host heterogeneity are more important in determining parasite virulence than the parasite characteristics. This does not invalidate modern theories of parasite evolution but suggests that variation in both hosts and parasites must be taken into account in more detail.

Haemodialysis or renal transplantation in the treatment of end-stage diabetic nephropathy.

We have reviewed 27 diabetic patients treated between 1971 and 1981 by haemodialysis and/or by transplantation. Overall patient survival is 43 per cent at five years (vs 78 per cent in non-diabetics of similar age). Two year patient survival is identical (73%) with haemodialysis and after transplantation. One year graft survival is 55 per cent. Progression of extrarenal diabetic complications is similar in haemodialysis and after transplantation. Recurrence of diabetic glomerulosclerosis was documented in two grafts. Haemodialysis thus offers a suitable alternative for diabetic patients who cannot be transplanted.

[Results of dialysis and transplantation in the treatment of patients with diabetic renal failure ]. / Résultats de l'hémodialyse chronique et de la transplantation rénale dans le traitement d l'urémie terminale du diabétique.

The respective merits of hemodialysis (HD) and transplantation (TP) in the treatment of 25 patients with diabetic renal failure are analyzed. Overall patient survival whatever the method of treatment is 72% at one year and 50% at 4 years. One year survival is 67% for patients treated only by HD and 81% after TP. This difference results in part from the fact that early death after the initiation of therapy occurs usually during HD prior to TP. Death results mainly from cardiovascular disease (6/7 deaths) in HD and from infectious complications (5/9 deaths) after TP. Taken together with death, rejection of 11/19 grafts reduces graft survival to 56% at one year and 33% at 2 years. Progression of cardiovascular, ocular and neurologic complications is similar whatever the mode of treatment. Recurrence of diabetic renal disease was documented in the graft of one patient. All patients with a 2 year survival (6 grafted, 1 dialyzed) have an excellent rehabilitation. Altogether both methods of treatment appear satisfactory. The initial pessimism regarding the outcome of HD treatment appears unwarranted. Unfortunately, both HD and TP remain marred by a greater number of complications in diabetic than in non-diabetic patients. Initiation of therapy at an earlier stage of the disease and better control of the diabetes might further improve results.