Synthesis of new fluoroquinolones and evaluation of their in vitro activity on Toxoplasma gondii and Plasmodium spp

The synthesis of four new computer-designed fluoroquinolones which have been predicted by QSAR analysis to be active against the protozoa Toxoplasma gondii is described. These compounds are inhibitory in vitro for T. gondii. One of these compounds has a remarkably high activity comparable to that of trovafloxacin. It combines the basic cyclopropyl-quinoline structure of gatifloxacin or moxifloxacin with the C-7 6-amino-3-azabicyclo[3.1.0]hexyl side chain of trovafloxacin. The four compounds are also inhibitory for blood stages of Plasmodium falciparum though at high concentration. These results confirm the potential of quinolones as anti-T. gondii and antimalarial drugs but also show that the QSAR models for T. gondii cannot be reliably extended for screening antimalarial activity.

Histopathological observations in new and classic models of experimental Schistosoma haematobium infections

The authors present marsh rat Holochilus brasiliensis, jirds Meriones shawi and M. unguiculatus as new models of Schistosoma haematobium infection. Histological findings were compared with those of classic models mouse Mus and hamster Mesocricetus. In new models, embryonated eggs were seen in the stool from 90 days post infestation (DPI) and active disease developed from 117 to 175 DPI. Seven out of 10 rodents presented granulomatous and/or chronic cystitis, fibrosis, polyps and urothelial changes: squamous metaplasia, precancerous dysplasia and squamous cell carcinoma of the urinary bladder. In the digestive tract of all new models, granulomas eroded the mucosa, formed inflammatory polyps, infiltrated the wall and accumulated into bilharziomas. In the liver, granulomatous hepatitis surrounded by bilharzial pigment deposit was apparent. Pipe-stem fibrosis involved 4 rodents with precirrhotic changes in 1 and portal hypertension in 2. One female Meriones suffered from granulomatous endometritis and salpingitis. All new models developed pulmonary granulomatosis with associated vascular lesions: giant cell arteritis in 1 rodent, thromboses in 3 and pulmonary hypertension in 4 others. In classic models, 1 Mus presented a squamous cell carcinoma of the urinary bladder while Mesocricetus displayed diverse lesions in digestive and genital tracts, liver and lungs. All tissue lesions, resembling those seen in humans in all points, were far more frequent and severe in new models than in classic ones. Those involving the urinary bladder have never been reported in other models such as monkeys: Pan troglodytes, Cercopithecus aethiops and Cebus apella. A comparison was carried out between different models on the basis of experimental conditions: definitive hosts, number of cercariae used, type and duration of infection. This study clearly demonstrated that Holochilus brasiliensis, Meriones shawi and M. unguiculatus are perfectly adequate models in terms of laboratory facilities. They are helpful in investigating the pathogenic mechanism of some disorders in S. haematobium infection, particularly tumours of the urinary bladder, and this may enhance therapeutic assays.

[Epidemiological study of Paragonimus sp. in south Cameroon]

A study was carried out in 1993 in south Cameroon in order to assess the changes in the incidence rate of human paragonimiasis, and to get information on the transmission pattern of Paragonimus sp. Two human cases have been recorded, and one dog was found infected in the Ntem Valley. The results suggest that a decrease of the incidence rate of paragonimiasis occurred in humans and animals. Paragonimus metacercariae were found in three species of freshwater crabs: Sudanonautes africanus, S. aubryi et S. granulatus, the latter being a new host. Prevalence of infection in crabs increased southerly, and significant seasonal changes were found. Two cats were infested with metacercariae from S. africanus, and studies are in progress to identify the parasite(s) at a specific level.

Speed of skin penetration and initial migration route of infective larvae of Schistosoma haematobium in Meriones unguiculatus

The kinetics of skin penetration of Schistosoma haematobium (Bilharz, 1852) (Trematoda, Schistosomatidae) cercariae is reported for the first time, Meriones unguiculatus (Rodent, Gerbillidae) being used as experimental model. It has been demonstrated that the cercariae cross the epidermis of their hosts either directly or through hair follicles culs-de-sac from 3 to 5 min. The corresponding schistosomulae slide into the superficial part of the dermis or move along the base of hair follicles. Six minutes after, schistosomulae are found in the lumen of lymphatic vessels running alongside blood capillaries. One hour post-infestation, the dermis presents acute inflammatory reaction with edema, infiltration of neutrophil and eosinophil leukocytes. Conversely, dilated blood capillaries do not contain any schistosomula. Thus, the initial migration path of infective larvae of S. haematobium in M. unguiculatus is lymphatic.