Clinical aspects of infection with Trichinella spp.

Isolated cases and outbreaks of infection with Trichinella spp. occur frequently throughout the world, sometimes resulting in fatalities. The clinical presentations of signs and symptoms are remarkably constant for most of the species of Trichinella, but in infections with Trichinella nativa and Trichinella britovi, classical symptoms of trichinellosis may be absent. It is important to be able to correlate the clinical presentation of trichinellosis with the life cycle of these helminths in order to make an accurate diagnosis. Knowledge of the epidemiology of the disease enables the physician to identify other potential cases, since most epidemics can be traced back to a common source of raw or undercooked meat. A comprehensive summary relating the most important clinical variables is presented graphically for easy reference to the text. Symptoms and signs are considered in relation to severity of infection. Laboratory findings and diagnostic techniques, including new modalities (e.g., DNA and antigen detection), are discussed. A discussion of treatment and preventive measures concludes our review.

Trichinosis: a prospective controlled study of patients ten years after acute infection.

The existence of chronic trichinosis as a disease entity is still a matter of debate. For 10 years after an outbreak of infection with Trichinella spiralis, we conducted a prospective controlled study of the patients involved. At the termination of this investigation, we undertook clinical, biochemical, serological, immunologic, neuroradiological, radiological, and psychological studies of 128 originally infected persons and 16 controls. The categories of symptoms most often documented in persons who had been infected were muscular (90%), ocular (59%), neurological (52%), and psychological (52%). Impaired muscle strength (56%), conjunctivitis (55%), and impaired coordination (32%) were the clinical manifestations most frequently encountered. Thirty-eight percent of the 128 originally infected patients still had IgG antibodies to T. spiralis after 10 years. Magnetic resonance imaging of the brain revealed no abnormalities. No calcifications of residual larvae were detected by mammography or muscle biopsy. The level of performance in psychometric tests was lower in the originally infected population than in the general population. Although patients who had had trichinosis differed significantly from controls in terms of a variety of parameters even after 10 years, we found insufficient evidence on which to conclude that chronic trichinosis exists as a distinct entity.

The role of muscle larvae of Trichinella spiralis in the behavioral alterations of the mouse host.

The effects of early and encysted muscle larvae of Trichinella spiralis on the open-field behavior of CD-1 mice were studied. Chemotherapy with fenbendazole prior to encystment of larvae prevented the development of behavioral changes in mice. The chemotherapeutic destruction of encysted muscle larvae restored the ambulatory activity of mice to normal levels. The study suggests that muscle larvae are the etiological agents of behavioral alterations in the mouse host.

The effect of the intestinal phase of Trichinella spiralis on the open-field behavior of mice.

The study assessed the impact of the adult phase of Trichinella spiralis on the open-field behavior of mice. Thiabendazole treatment was used to chemosterilize adult worms in vivo. Untreated mice exhibited a marked decline in their ambulatory and exploratory activities (from day 14 post-infection until the end of the experiment). In contrast, infected mice treated with thiabendazole did not exhibit any behavioral alterations. This suggested that the adult phase of T. spiralis did not contribute to behavioral pathology in the mouse host.

Loss of behavioural dominance in male mice infected with Trichinella spiralis.

Trichinella spiralis infections may lead to the loss of behavioural dominance among male mice. Reversals of dominance order first appear at the time when newborn larvae are released into the circulation of the host. The duration of dominance reversals bears no relationship to the number of muscle larvae harboured.

The open-field behaviour of mice infected with Trichinella spiralis.

The behaviour of mice exposed to graded doses of Trichinella spiralis larvae was monitored in an open-field situation. Ambulatory and exploratory activity declined significantly as the infections progressed, whereas the time spent inactive increased concomitantly. The advent of these behavioural changes coincided with the expected release of larvae by the adult worms and showed no clear signs of abating as late as 90 days post-inoculation. The levels of activity were negatively correlated with the inoculating dose. Such behavioural changes may render the host more vulnerable to predation and thus enhance parasite transmission.

Establishment and maintenance of behavioural dominance in male mice infected with Trichinella spiralis.

Trichinella spiralis infections influenced the establishment and maintenance of behavioural dominance among outbred male mice. Infected animals assumed a subordinate status when challenged by normal or more lightly infected conspecifics both in an unfamiliar test arena and in their established home cages. These effects were demonstrable during the acute and the chronic phases of infection. The significance of this phenomenon to the survival of the mouse host and the transmission of the parasite is discussed.