A test system previously described by Blom et al (1993) was used to investigate the preference of the Mongolian gerbil (Meriones unguiculatus) with respect to light intensity in their cage, by comparing a standard transparent rodent cage with three cages darkened by either 25, 50 or 75 per cent. The ten animals included in the test spent most of their time in the cages that were darkened by 50 and 75 per cent, thus relatively avoiding the standard cage. Preference was mainly determined by visits longer than 15min and was therefore possibly associated with sleeping behaviour. Food and water consumption were not restricted to the preferred cages.

These results imply that gerbils should be housed preferably in cages that allow sheltering in relatively dark places. For this purpose, placing shelter objects in the cage should be considered.

The biological and genetic diversity of Neospora caninum is very limited because of availability of only a few viable isolates worldwide. This study describes the isolation and biological and molecular characterization of a new viable isolate of N. caninum (NC-SP1), from a cattle in Brazil. Approximately 400 g of brain from a naturally infected adult male cattle from an abattoir was fed to a 2-month-old dog. Neospora-like oocysts were observed on day 7 post-inoculation (PI) and the duration of oocyst shedding was 14 days. The DNA obtained from oocysts was characterized molecularly and the final sequence was 99% identical to homologous sequences of N. caninum available in GenBank®. For bioassay, gerbils (Meriones unguiculatus) were orally inoculated with 10 100 and 1000 oocysts; all gerbils remained clinically normal but developed N. caninum antibodies 14 days PI. Cell culture isolation was successful using the brain homogenate from one of the gerbils and tachyzoites were observed 24 days PI. Microsatellite genotyping revealed a unique genetic profile for this new reference isolate.

There is a general lack of knowledge regarding the absorption and tissue storage of the provitamin A carotenoid β-cryptoxanthin. The present study investigated the whole-body tissue distribution of β-cryptoxanthin in an appropriate small animal model, the Mongolian gerbil (Meriones unguiculatus), for human provitamin A carotenoid metabolism. After 5 d of carotenoid depletion, five gerbils were euthanised for baseline measurements. The remaining gerbils were placed in three weight-matched treatment groups (n 8). All the groups received 20 μg/d of β-cryptoxanthin from tangerine concentrate, while the second and third groups received an additional 20 and 40 μg/d of pure β-cryptoxanthin (CX40 and CX60), respectively, for 21 d. During the last 2 d of the study, urine and faecal samples of two gerbils from each treatment group were collected. β-Cryptoxanthin was detected in the whole blood, and in twelve of the fourteen tissues analysed. Most tissues resembled the liver, in which the concentrations of β-cryptoxanthin were significantly higher in the CX60 (17·8 (sem 0·7) μg/organ; P= 0·004) and CX40 (16·2 (sem 0·9) μg/organ; P= 0·006) groups than in the CX20 group (13·3 (sem 0·4) μg/organ). However, in intestinal tissues, the concentrations of β-cryptoxanthin increased only in the CX60 group. Despite elevated vitamin A concentrations in tissues at baseline due to pre-study diets containing high levels of vitamin A, β-cryptoxanthin maintained those vitamin A stores. These results indicate that β-cryptoxanthin is stored in many tissues, potentially suggesting that its functions are widespread.

Neurocysticercosis is a public health problem in many developing countries and is the most frequent parasitic disease of the brain. The human tapeworm carrier is the main risk factor for acquiring neurocysticercosis. Since the parasite lodges only in the human intestine, experimental models of Taenia solium taeniosis have been explored. Macaques, pigs, dogs, cats and rabbits are unsuccessful hosts even in immunodepressed status. By contrast, rodents are adequate hosts since tapeworms with mature, pregravid and, in some cases, gravid proglottids develop after infection. In this review, information that has been generated with experimental models of taeniosis due to T. solium is discussed. Initially, the use of the model for immunodiagnosis of human taeniosis and evaluation of intervention measures is summarized. Next, descriptions of tapeworms and comparison of hamsters, gerbils and other mammals as experimental models are discussed, as well as data on the humoral immune response, the inflammatory reaction and the production of cytokines associated to Th1 and Th2 responses in the intestinal mucosa. Finally, evaluation of protection induced against the development of tapeworms by recombinant T. solium calreticulin in hamsters is summarized and compared to other studies.

Vitamin A (VA) deficiency is a worldwide public health problem. Biofortifying existing sources of β-carotene (βC) and increasing dietary βC could help combat the issue. Two studies were performed to investigate the relative βC bioavailability of a βC supplement to purple, high-βC orange, and typical orange carrots using Mongolian gerbils (Meriones unguiculatus). In study 1, which used a traditional bioavailability design, gerbils (n32) received a diet containing orange, purple, or white carrot powder, or white carrot powder +a βC supplement. In study 2, which included βC-biofortified carrots, gerbils (n 39) received orange, high-βC orange, purple, or white carrot powder in their diet. Both studies lasted 21 d and the gerbils were killed to determine the effect of carrot type or supplement on serum and liver βC, α-carotene, and VA concentrations. Liver stores of βC or VA in the gerbils did not differ between orange and purple carrot diets when equal amounts of βC from each of the diets were consumed (P>0·05). Both the orange and purple carrot diet resulted in higher liver VA compared with the supplement (P<0·05). High-βC carrots resulted in more than 2-fold higher βC and 1·1 times greater VA liver stores compared with typical orange carrots (P<0·05). These results suggest that high-βC carrots may be an alternative source of VA to typical carrots in areas of VA deficiency. Second, phenolics including anthocyanins and phenolic acids in purple carrot do not interfere with the bioavailability of βC from purple carrots.

Testicular activity of wild and laboratory strains of Meriones unguiculatus and its seasonal dependence was studied. Comparative intraspecific measurements were performed in adult males of the laboratory strain (LAB) and in male offspring of wild Mongolian gerbils (WF-1 to WF-3). All animals were reared under identical conditions including a constant light regime. LAB and WILD were examined in January, July and October. Testicular spermatozoa were counted, proportions of different cell types were analysed using DNA flow cytometry, and total germ cell transformation was calculated from DNA histograms. Intratesticular testosterone concentrations were measured with an enzyme immunoassay. The results showed that differences of testicular activity are dependent on the season as well as the strain and the generation. The season affected testicular parameters in LAB resulting in lowered testosterone and sperm production in July and October, respectively. In contrast, all testicular cell parameters were significantly lower for WF-1 in January compared with October. These seasonal differences were neutralized or diminished in WF-2 and WF-3. In the WILD, total testicular activity was lower and varied more in all months studied, but the differences compared with the values in LAB decreased in the successive generations. WF-3 showed the lowest discrepancy of testis weight and spermatogenic output compared with LAB. The data suggest endogenous cues for seasonal regulation of spermatogenesis, but this endogenous rhythm seems to be subsided or lost rapidly. These findings indicate rapid, adaptive changes in the early offspring generations from wild populations during breeding in the laboratory.

A new strain of wild Meriones unguiculatus (strain Ugoe:MU95, named WILD) with high genetic variability was recently established in Germany. A previous study showed that offspring (F-1) of WILD founders (F-0) showed reduced spermatogenesis and testosterone compared to domesticated gerbils (LAB) maintained under similar conditions. We investigated F-0 and subsequent generations in respect to sexual maturation, duration of fertility and gonadal weights of different seasons. Body and reproductive organ weights showed negligible seasonal fluctuations in both strains. Testis and epididymis weights in WILD covered a wide range, which indicates a high reproductive variability. Reproductive organ weights increased in F-3. Less variable and high reproductive organ weights (testis >900 mg, epididymis >200 mg) in almost all LAB illustrate their readiness to reproduce, even in small individuals. Prominent testis (T+) was found in 71% of adult males (F-1, F-2) reflecting the natural portion of T+(63%) found in wild gerbils investigated in Mongolia in 1995 and 2002. Testicular descent was accelerated and pronounced in WILD F-3 (T+, 88%) and LAB (T+, 91%). Time between mating and the first litter was significantly longer in wild F-0 than in their offspring or LAB. The average age in wild F-0 when the last litter was born was 27 months. Breeding went on for 2 to 32 months and was mostly terminated by the death of the females. Relative testis and epididymis weights correspond in young adults and in old males up to 6 years, the total life span of male wild Mongolian gerbils. In summary, the results suggest that laboratory conditions improve the reproductive fitness of wild gerbils.

A species of Besnoitia from naturally infected rabbits from Argentina was propagated experimentally in mice, gerbils, rabbits, cats, and cell cultures. Cats fed tissue cysts from rabbits shed oocysts with a prepatent period of nine to 13 days. Sporulated oocysts were infective to gerbils, rabbits, outbred Swiss Webster and interferon gamma gene knockout mice. Bradyzoites were infective orally to gerbils and cats. Tachyzoites were successfully cultivated and maintained in vitro in bovine monocytes and African green monkey kidney cells. Schizonts were seen in the lamina propria of the small intestine of cats fed tissue cysts; the largest ones measured 52×45 μm. Schizonts were also present in mesenteric lymph nodes, livers, and other extra-intestinal organs of cats fed tissue cysts. Oocysts were 10–14×10–13 μm in size. This rabbit-derived species of Besnoitia resembled B. darlingi of the North American opossum, Didelphis virginiana with an opossum-cat cycle, but it was not transmissible to D. virginiana, and B. darlingi of opossums was not transmissible to rabbits. Based on biological, serological, antigenic, and molecular differences between the rabbit and the opossum Besnoitia, a new name, B. oryctofelisi is proposed for the parasite from domestic rabbits from Argentina.

Animals were trapped in Marigat, Baringo District to investigate animal reservoirs of visceral leishmaniasis in an endemic focus of the disease. Several species of rodents, carnivores and reptiles were captured. Specimens of spleen, liver and blood tissues were taken from the animals. The specimens were triturated into sterile saline and then cultured into NNN medium, and some of it injected into hamsters intraperitoneally. Skin biopsies were also taken and cultured in NNN medium. Slide smears of all the tissues taken were made stained with Giemsa stain and examined under the microscope for amastigotes. Four isolates of leishmanial parasites were made from a gerbil and three monitor lizards.