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Biomedical subjects

J D MacLean

Publications and source records attributed to J D MacLean.

At least 55 records · Page 3Linked to original sources
PubMed1988

Imported rickettsial disease: clinical and epidemiologic features.

PURPOSE AND METHODS: The rickettsioses continue to constitute major health problems in many parts of the world. With increasing international travel, recognition of rickettsial diseases by physicians is becoming more important. The clinical features of four cases of rickettsial disease imported into Canada over a five-year period are presented; two patients with tick typhus (Rickettsia conorii), one patient with scrub typhus (R. tsutsugamushi), and one patient with murine typhus (R. typhi). We also present the North American data over the past 10 years from the Centers for Disease Control (CDC) (Atlanta). RESULTS: Since 1983 in the United States, three cases of imported scrub typhus, all after travel to India, were confirmed, as well as six cases of murine typhus after travel to southeast Asia. At the CDC, 67 imported cases of tick typhus have been confirmed by indirect fluorescent antibody test since 1976; most illnesses occurred after travel to Africa. CONCLUSION: Rickettsial diseases are underrecognized by physicians, who should consider these diagnoses in travelers returning from endemic areas. Since effective treatment is available, prompt diagnosis and treatment are important. In all cases, specific serologic confirmation should be obtained.

Adult↗
PubMed1987

Cortisone-induced recrudescence of Giardia lamblia infections in gerbils.

The course of infection with Giardia lamblia in gerbils was studied after oral inoculation with either cysts isolated from humans or cultured trophozoites. Primary infections occurred in 87% of exposed gerbils; cyst release peaked during the second and third weeks post-infection; cysts and trophozoites were observed for up to 49 and 87 days post-infection, respectively. Gerbils were refractory to challenge infection with infective human source cysts at 5 months post-infection. Overall, 50% of animals given subcutaneous injections of hydrocortisone acetate, during or following the late stages of their primary infection, showed recrudescence of infection as evidenced by passage of cysts; percentages showing recrudescence were: 80% at 50 days post-infection, 55% at 70 days post-infection, 27% at 7 months post-infection, and 50% (2 of 4) in gerbils challenged unsuccessfully at 5 months post-infection and subsequently injected with hydrocortisone acetate at 7 months post-infection. Both infected animals and uninfected controls injected with hydrocortisone acetate were immunocompromised as evidenced by significantly reduced plaque forming cell responses to sheep red blood cells. We conclude that infections with G. lamblia in gerbils can last longer than standard examinations for cysts would indicate, and that long-term immunity to this organism can be nonsterile.

Animals↗
PubMed1986

Arctic trichinosis presenting as prolonged diarrhea.

We describe an outbreak of trichinosis after the consumption of raw walrus meat in 10 Inuit inhabitants of a northern community. During the presentation of the illness, diarrhea was found in all subjects and was the dominant symptom in 8 of the 10 cases. Myalgia (60%) and muscle weakness (50%) were much less prominent complaints. The diarrhea was characteristically prolonged, lasting up to 14 wk (average 5.8 wk), as opposed to comparatively short episodes of myalgia (average 5.4 days) and muscle weakness (average 4.5 days). Prolonged diarrhea with little or no muscle symptomatology in an epidemic form represents a previously unrecognized clinical presentation of trichinosis. It remains to be determined whether this new clinical presentation is related to variant biological behavior of arctic Trichinella, to previous exposure to the parasite, or to other factors.

Adult↗
PubMed1986

Neurocysticercosis: surgical and medical management with praziquantel.

Eight cases of neurocysticercosis were encountered at the two major neurological centers affiliated with McGill University in Montreal in 4 years. All patients were immigrants who had been in Canada for a period of 1 to 18 years and came from South America (three cases), Haiti (three cases), and Greece (two cases). Five patients had parenchymal cysts and presented with epilepsy; three had the racemose form and presented with hydrocephalus. Four patients with parenchymal cysts were treated by removal of the cysticercus and did well. One patient with numerous cysts was treated with praziquantel with good clinical and radiological results. Two patients with the racemose form were treated by cyst aspiration, cerebrospinal fluid (CSF) diversion, and praziquantel and did well. Another patient with the racemose form, seen before the advent of praziquantel, died of cysticercosis infection. Neurocysticercosis is not uncommon in the immigrant population of large North American cities. Single symptomatic cysts can be evacuated surgically with good results; multiple parenchymatous cysts can be treated with praziquantel. Patients with the racemose form who are treated with CSF diversion and praziquantel do well, although those who are only treated surgically die of their disease.

Adult↗
PubMed1986

The effects of cyclosporin A on the course of infection with Giardia muris in mice.

Administration of cyclosporin A (CyA) to mice prior to infection and at weekly intervals during the infection with Giardia muris resulted in an increase in cyst output and a delay of the elimination phase of the infection. A short term treatment (4 days) of infected mice with CyA induced a significantly higher cyst release after treatment. CyA did not affect the ability of immune mice to resist reinfection. Our findings indicate that CyA has compromised immunological control of the primary Giardia infection, but not the ability of the immune host to resist reinfection. We propose that the use of immunosuppressive drugs may be a contributing factor in transmission of giardiasis.

Animals↗
PubMed1985

Giardia muris-induced depression of the primary immune response in spleen and mesenteric lymph node cell cultures to sheep red blood cells.

Primary in vitro plaque-forming cell (PFC) responses to sheep red blood cells (SRBC) were examined for spleen and mesenteric lymph node (MLN) cell populations from susceptible (A/J) and resistant (B10.A) mice during the infection with Giardia muris. Spleen and MLN cells isolated from mice during the acute phase of the infection were less responsive to SRBC in vitro than those from uninfected mice. Depressed anti-SRBC PFC response was detected earlier and was more pronounced in MLN cell cultures when compared to the response of spleen cell cultures. Spleen and MLN cells from donors infected with G. muris for 15 days had the capacity of depressing PFC response to SRBC of cells isolated from uninfected mice. This suppressor activity was localized in the plastic-adherent fraction of spleen cell populations isolated from A/J and B10.A mice. Since G. muris is a gastro-intestinal infection of mice, lower capacity of the MLN cells to respond to an antigenic stimulation in vitro may explain, in part, the proliferation of the trophozoites during the acute phase of the infection.

Animals↗
PubMed1985

Suppression of primary antibody response to sheep erythrocytes in susceptible and resistant mice infected with Giardia muris.

The kinetics of anti-sheep erythrocyte (SRBC) response were studied in susceptible (A/J) and resistant (B10.A) mice during infection with Giardia muris. Mice infected with G. muris were found to be less responsive to either intraperitoneally or intraduodenally administered SRBC. Immunodepression was of relatively short duration, occurring during the period of highest trophozoite density in the small intestine, and was present in both spleen and, in particular, mesenteric lymph node cell populations. The main difference in the kinetics of anti-SRBC responses between A/J and B10.A mice was that susceptible mice were significantly less responsive to SRBCs than were the resistant B10.A animals. The difference in the kinetics of the anti-SRBC response between A/J and B10.A mice was not due to T-suppressor cell activity. Mesenteric lymph node cell transfers but not spleen cell transfers from infected mice to syngeneic recipients caused depressed normal anti-SRBC response. Furthermore, administration of the soluble extract of the trophozoites to uninfected mice resulted in a depressed response against SRBCs. Pronounced immunodepression in gut-associated lymphoid tissues may be more relevant than systemic immunodepression to survival and reproduction of trophozoites in murine giardiasis.

Animals↗
PubMed1984

Susceptibility and resistance of inbred mice to Giardia muris.

The susceptibility and resistance of inbred mice to Giardia muris was studied during the acute and elimination phases of infection. The infection in susceptible A/J and C3H/He mice was characterized by a short latent period, high cyst output during the acute phase of infection, and prolonged periods of cyst release. In contrast, resistant B10.A and DBA/2 mice had a longer latent period, a lower cyst output during the acute phase, and relatively rapid resolution of infection. The trait of susceptibility and resistance during both acute and elimination phases of the infection was found to be under complex multigenic control as determined by examination of the response of F1 hybrid mice and backcross analyses. The genes controlling this trait did not appear to be linked to the H-2 locus. In addition, the control of the response of mice to G. muris during the acute phase of infection was probably mediated by mechanisms independent from those controlling the response during the elimination phase of infection.

Acute Disease↗
PubMed1984

Three cases of schistosomiasis mekongi from northern Laos.

Three cases of intestinal schistosomiasis acquired in northern Laos are reported. All three patients swam regularly for many years in the Mekong River near the cities of Vientiane and Luang Prabang. Morphology of the eggs found on rectal biopsy indicated infection with Schistosoma mekongi. One patient had severe portal hypertension with bleeding esophageal varices requiring a splenorenal shunt; studies of her liver biopsy showed S. mekongi eggs and periportal fibrosis. A second patient had abnormal liver function tests, and a third patient was asymptomatic. In two of the three cases, no schistosome eggs were found on stool examination, and the diagnosis was made by rectal biopsy. The implications of this new focus of infection are discussed.

Adult↗
PubMed1984

Observations on natural and experimental infections with Giardia isolated from cats.

The course of infection with Giardia was studied in (a) naturally infected cats and (b) experimentally infected Mongolian gerbils using Giardia cysts isolated from cats. Natural infection was characterized by: (a) a latent period of 11 to 13 days, (b) the pattern of cyst release which was either continuous or intermittent during the acute phase of infection and (c) elimination of the infection in four to five weeks after exposure. Mongolian gerbils were found to be susceptible to infection with Giardia isolated from cats. The course of infection in gerbils was characterized by intermittent cyst release and elimination of the infection in about three weeks. The pattern of cyst release in gerbils infected with Giardia isolated from cats was similar to the previously reported pattern of cyst release in gerbils infected with Giardia isolated from humans. The possible role of pets in the zoonotic transmission of giardiasis is discussed.

Animals↗
PubMed1983

Giardia lamblia infections in Mongolian gerbils: an animal model.

Mongolian gerbils were susceptible to infection with Giardia lamblia cysts from patients. Inoculation of gerbils with 5 x 10(3) cysts each resulted in an infection characterized by the intermittent release of cysts for up to 39 days. The mean number of cysts released per gerbil in a 2-hr period was 8.8 x 10(2) (range, 0-5 x 10(3)). The highest number of trophozoites found in the intestine was on day 15 after infection, when the mean number of trophozoites per gerbil was 6.36 x 10(6). Administration of cysts from different patients to gerbils resulted in a similar pattern of cyst release during the first 30 days of infection. Mongolian gerbils were also susceptible to infection with cultured trophozoites (Portland 1 strain). The pattern of cyst release and the number of trophozoites in the intestines of orally and duodenally inoculated gerbils were similar. Gerbils were protected against reinfection with G. lamblia for up to eight months after primary infection.

Animals↗
PubMed1983

Comparative studies on the pattern of infection with Giardia spp. in mongolian gerbils.

Mongolian gerbils (Meriones unguiculatus) were inoculated with known numbers of Giardia cysts isolated from humans, beavers and mice. The pattern of cyst release in the feces was studied for a period of 35 days. After a latent period of 5 days, animals infected with G. muris release cysts in their feces every day until day 14. Gerbils infected with human or beaver isolates released cysts in their feces intermittently for 30 days. These results indicated that the mode of cyst release in these animals was characteristic of the parasite, and was independent of the host. Mongolian gerbils acquire complete resistance upon homologous species challenge but demonstrate only partial protection when challenged with a different species of Giardia. We concluded that the Mongolian gerbil model could be useful in epidemiological studies for two reasons: it can be used for determination of cyst viability, and for the identification of the etiological agent.

Animals↗
PubMed1979

Subcutaneous dirofilariasis in Okinawa, Japan.

A nematode within a subcutaneous nodule excised from an elderly Okinawan man has been tentatively identified in sections as an immature Dirofilaria repens--the first to be reported from Japan.

Aged↗