Mastomys natalensis as an experimental host for Brugia malaye subperiodic.

Infective larvae of Brugia malayi subperiodic obtained by dissection of infected Aedes togoi were injected subcutaneously into the scrotal region of Mastomys natalensis. From altogether 58 infected male M. natalensis 81% showed consistently or intermittently detectable microfilaraemia, whereas in 19% of the animals no microfilaraemia could be detected at any stage. The mean prepatent period was 136 days; the microfilarial density varied from 1 to 535 per 20 c. mm blood. In those animlas with consistently detectable and in general higher microfilaraemia an average of 13.1 live adult worms were found, against an average of 6.4 adult worms in animals with intermittent detectable and in general lower microfilaraemia. An average of 1.5 worms was found in animals which at no stage showed detectable microfilaraemia. A correlation between worm burden and prepatent period could be observed in the individual groups. From the total of 520 live adult worms recovered at necropsy, 37% were found in the lungs, 29% in the parenchyma of the testes and 34% in the lymphatic system. 47% of live fertile female worms were found in the lymphatic system, whereas the majority, i.e; 52% of infertile female worms were detected in the lungs. In addition, 380 encapsulated dead worms were found, most of them (98%) in the lymphatic system. 61% of a total of 900 live and dead worms were found in the region of the lymphatic system.     

On Dipetalonema viteae infection of Mastomys natalensis

Experimental infections were carried out with the tissue-dwelling filaria Dipetalonema viteae using the argasid tick Ornithodorus moubata as the intermediate and the multimammate rat Mastomys natalensis (Strain GRA Giessen) as the final host. The optimum infective dose was found to be 50 third-stage larvae, which produced patent infections and the recovery rates of adult parasites were 47.6 and 26.4% of the inoculated larvae 140 and 189 days after infection, respectively. After an average prepatent period of 57 days, the microfilaraemia increased progressively and reached relatively low maximum values about 192 days after infection. These maximum values were followed by rapid decrease of microfilaraemia, but microfilariae were still detectable at 261 days post infection. Following the subcutaneous injection of infected animals with dexamethasone in single doses each of 1, 10 or 20 mg/kg body weight 30 minutes before blood puncture, a dose-dependent increase in the microfilarial counts in the circulating blood was observed, this reaching maximum values between 120 and 160 days after infection. Repeated administration of single doses of 10 mg/kg dexamethasone revealed an uniform but temporary increase in the microfilaraemia but this was not associated with any alterations in the reproductive organs of adult female parasites. No correlation could be found between the number of microfilariae in the circulating blood and the number of adult worms recovered from the subcutaneous connective tissue. At necropsy 300 days after infection living female parasites could not be found any more.     

Experimental infections of the multimammate rat (Mastomys natalensis) with Leishmania donovani and Leishmania major

The susceptibility of the multimammate rat, Mastomys natalensis, to experimental infections with Leishmania donovani and L. major was examined. Inoculations of L. major promastigotes into the skin resulted in nonulcerating lesions in which parasites could be detected for more than 30 weeks later. Intravenous inoculations of L. donovani promastigotes produced visceral infections characterized by a continuing increase in splenic parasite burdens and liver parasite burdens which peaked during the first few weeks of infection and gradually decreased as the disease became chronic. L. donovani could be isolated from the blood throughout the infection, and promastigotes were cultured from the spleens of rats inoculated intradermally. Thus, the multimammate rat appears to be a good reservoir host for these parasites.     

Filarial infections in travelers and immigrants

Filarial infections including loiasis, onchocerciasis, and lymphatic filariasis are important causes of morbidity in endemic populations worldwide, and they present a risk to travelers to endemic areas. Definitive diagnosis is complicated by overlap in the geographic distribution and clinical manifestations of the different filarial parasites, as well as similarities in their antigenic and nucleic acid composition. This has important implications for treatment, because the efficacies and toxicities of available antifilarial agents differ dramatically among filarial species. Recent advances, including the visualization of adult filarial worms in vivo by high-frequency ultrasound and the identification of the bacterial endosymbiont, Wolbachia, have greatly improved our understanding of the pathogenesis of filarial infection and have led to novel approaches to the diagnosis and treatment of travelers and immigrants from filarial-endemic regions.     

Hematology and Clinical Chemistry Reference Ranges for Laboratory-Bred Natal Multimammate Mice (Mastomys natalensis)

Laboratory-controlled physiological data for the multimammate rat (Mastomys natalensis) are scarce, despite this species being a known reservoir and vector for zoonotic viruses, including the highly pathogenic Lassa virus, as well as other arenaviruses and many species of bacteria. For this reason, M. natalensis is an important rodent for the study of host-virus interactions within laboratory settings. Herein, we provide basic blood parameters for age- and sex-distributed animals in regards to blood counts, cell phenotypes and serum chemistry of a specific-pathogen-monitored M. natalensis breeding colony, to facilitate scientific insight into this important and widespread rodent species.     

Shared antigens between Litomosoides carinii and its hosts Sigmodon hispidus and Mastomys natalensis

Using a indirect immunofluorescent technique it has been shown that host or host-like antigens are present on adults and microfilariae of Litomosoides carinii from cotton rats and multimammate rats. Red blood cell components were seldom detected on any stage but serum antigens were found associated with the cuticle of adults worms. Serum components were absent from in utero and in vitro microfilariae but were found on microfilariae from pleural exudate and host blood. These components were lost from microfilariae after their ingestion by the vector, were absent from third and fourth stage larvae but reappeared as the adults matured in the pleural cavity of a new host. Countercurrent immunoelectrophoresis showed that the components had alpha 2--beta 1 and beta 1--beta 2 mobility.     

Reproductive characteristics of Mastomys natalensis and Lassa virus prevalence in Guinea, West Africa

We recently reported increased prevalence of Lassa virus (LASV) infection in Mastomys natalensis during the rainy season in Guinea, West Africa. Here, the association of LASV prevalence with fecundity, fertility, and the age structure of the rodent population was analyzed using data from the previous study. The animals reproduced throughout the year, but highest fecundity was observed during the rainy season. Accordingly, the rodent population was aged at the beginning and young at the end of the rainy season. Lassa virus infection was observed in all age groups, including the very young, which is compatible with vertical transmission. However, since the prevalence of infection showed a trend with increasing age in the younger age groups, horizontal transmission by yet unknown mechanisms may also play a role in LASV transmission. Multivariate analysis did not show an association of LASV prevalence with any demographic variable studied. Rodent behavior influencing virus transmissibility and contaminated environment may therefore be responsible for spatial and seasonal variations in LASV prevalence in M. natalensis.     

Simultaneous infection of Mastomys natalensis with Dipetalonema witei and Litomosoides carinii (author's transl)

Mastomys natalensis that has been described by L?mmler et al. (1968) as suitable host for Litomosoides carinii can also serve as final host for Dipetalonema witei. At the end of the prepatency period the microfilaraemia increased as rapidly in Mastomys as in the original final host Meriones persicus. Maximal microfilaraemia was observed earlier in Mastomys (120 days p.inf.) than in Meriones (250 days p.inf.). Accordingly microfilariae counts decreased more rapidly in Mastomys. The maximal counts found in Mastomys was 78000 microfilariae/ml blood, which is 3.2 times less than in M. persicus. Furthermore it could be demonstrated that a simultaneous experimental infection of Mastomys with D. witei and L. carinii in possible. The course of microfilaraemia and the number of macrofilariae were comparable in mono- and simultaneous infections for both species of filariae. The macrofilariae of D. witei began to die earlier than those of L. carinii both in mono- and in simultaneous infections. The percentage of dead macrofilariae was 3.8% 110 days p.inf., and 13.1% 130 days p.inf. respectively. Therefore, chemotherapeutic experiments should be terminated and evaluated about 110 days p.inf.     

Attempts to infect Meriones unguiculatus and Mastomys natalensis with Wuchereria bancrofti from West Africa.

44 male and female Meriones unguiculatus and 13 male Mastomys natalensis were inoculated with infective stage larvae of Wuchereria bancrofti from West Africa and dissected between 16 and 360 days after inoculation. Fourth stage larvae of W. bancrofti were recovered in Meriones until the 90th day p.i. and in Mastomys until the 175th day p.i. The longest larva obtained from Meriones measured 9.5 mm and from Mastomys 6.5 mm.     

Chemotherapeutic studies on Litomosoides carinii infection of Mastomys natalensis. 7. Filaricidal activity of furazolidone

Investigations were carried out on the filaricidal activity of furazolidone against Litomosoides carinii infection in Mastomys natalensis. Oral administration of the drug in daily doses of 25, 50, 75, and 150 mg/kg body weight on 5 consecutive days revealed respectively 96,4, 99,3 and, with the two later doses, 100% reduction of macrofilariae in the pleural cavities, and produced a continuing dose-dependant decrease of microfilaraemia in the circulating blood. After oral doses of 5 x 50 mg/kg, all the adult parasites were killed within two weeks of the start of treatment and were found encapsulated in fibrinous masses in the pleural cavities. Deformed and degenerated embryonic stages could be seen in female worms as early as 3 days after the end of treatment. Furazolidone possesses a considerable chemotherapeutic index.