Hyperglycemics, hypoglycemics and glucose metabolism in Trypanosoma lewisi

Refractory hypoglycaemia in a dog infected with Trypanosoma congolense

A 20 kg German shepherd dog was presented to a French veterinary teaching hospital for seizures and hyperthermia. The dog had returned 1 month previously from a six-month stay in Senegal and sub-Saharan Africa. Biochemistry and haematology showed severe hypoglycaemia (0.12 g/L), anaemia and thrombocytopenia. Despite administration of large amounts of glucose (30 mL of 30% glucose IV and 10 mL of 70% sucrose by gavage tube hourly), 26 consecutive blood glucose measurements were below 0.25 g/L (except one). Routine cytological examination of blood smears revealed numerous free extracytoplasmic protozoa consistent with Trypanosoma congolense. PCR confirmed a Trypanosoma congolense forest-type infection. Treatment consisted of six injections of pentamidine at 48-hour intervals. Trypanosomes had disappeared from the blood smears four days following the first injection. Clinical improvement was correlated with the normalization of laboratory values. The infection relapsed twice and the dog was treated again; clinical signs and parasites disappeared and the dog was considered cured; however, 6 years after this incident, serological examination by ELISA T. congolense was positive. The status of this dog (infected or non-infected) remains unclear. Hypoglycaemia was the most notable clinical feature in this case. It was spectacular in its severity and in its refractory nature; glucose administration seemed only to feed the trypanosomes, indicating that treatment of hypoglycaemia may in fact have been detrimental.

Physiological relationships and circadian periodicities in rodent trypanosomes

Trypanosome circadian rhythms in rats infected with Trypanosoma lewisi and mice infected with T. duttoni (equals T. musculi) were observed. Peak numbers of trypanosomes were recorded at nightfall and fewest organisms seen at daybreak. Reversal of the photoperiod resulted in a comparable reversal of the trypanosome parasitaemia. Periodicities of blood glucose levels and circulating leucocytes were relatively similar in T. lewisi-infected rats to rhythms previously defined in normal aimals. In trypanosome-infected mice, circulating leucocytes had a peak at 1800 hours and were minimal at midnight. Immune serum and epinephrine apparently had opposite effects on numbers of circulating rat trypanosomes; antisera reduced and epinephrine increased the numbers. Increased motor activity appeared to induce increased parasitaemia. Results of these and other studies suggest that in diurnally active hosts, trypanosome periodicities are characterized by increasing numbers in the circulation throughout the day and reach a peak just before darkness. In nocturnally active animals a similar rhythm was observed with only a slight phase change; circulating trypanosomes increased throughout the day and were maximal soon after nocturnal onset.