Tropical diseases encountered in Canada: 1. Chagas' disease.

Chagas'' disease, or South American trypanosomiasis, is an endemic South American disease now being seen in Canada in both acute and chronic forms. It is characterized by an initial parasitemia that elicits a brisk immune response. Evidence is mounting that the debilitating chronic form, which is characterized by cardiac and visceral organ failure, results from antigenic cross-reactivity between the parasite and the human host, which generates an aberrant, destructive, cell-mediated immune response. Diagnosis, treatment and potential areas for investigation are discussed.     

Zoonotic diseases in Canada: an interdisciplinary challenge.

Although zoonotic diseases are generally rare in Canada, a wide range of pathogens can be transmitted from animal reservoirs to humans through insect vectors or direct contact with wild and domestic animals. Across the country researchers with backgrounds ranging from wildlife biology to parasitology and epidemiology are tracking a variety of zoonotic diseases, some of which are causing increasing concern among public health officials.     

Parasites and diseases of bison in Canada IV. Serologic survey for brucellosis in bison in northern Canada

Serum samples collected from 2,365 free-roaming hybrid bison (Bison bison bison x Bison bison athabascae) in Wood Buffalo National Park and adjacent areas in the Northwest Territories were tested for brucellosis during the period 1959 to 1974. A positive reaction was obtained in 739 (31.2%) of the animals tested. The overall effect of brucellosis on this free-roaming bison population is unknown. The authors also dealt with some of the actual and possible consequences of the disease in this population.     

Impact of vaccination on selected diseases in Canada

Vaccination has dramatically reduced the morbidity and mortality rates of a number of diseases. The crucial element of vaccination programs is commitment to widespread coverage and to containment of outbreaks. Vaccines have led to virtual elimination of poliomyelitis and promise to eliminate measles. The incidence of congenital rubella syndrome will probably only be diminished if vaccination is extended to all 1-year-olds and susceptible prepubertal girls. The employment of diphtheria toxoid is one of the great success stories in public health. The incidence of pertussis has declined because of the diphtheria-pertussis-tetanus (DPT) vaccine given to infants, although elimination of the disease will probably have to await development of a more potent pertussis antigen. A remarkable reduction in the incidence of tetanus and tuberculosis has also been achieved.     

Tropical ulcers.

We present 87 cases of chronic leg ulcers. The ages and sexes of the patients, and the symptomatology and complications, are described. The term "tropical ulcer" is inappropriate for these cases--though the term may be appropriate for certain rare acute ulcers colonized by Vincent's bacilli. For most persistent leg ulcers in the tropics, however, a general term of chronic ulcer is better--because it stimulates one to look for the cause and to treat the patient accordingly.