Experimental Haemonchus contortus infections in guinea pigs

Approximately 40% of exsheathed Haemonchus contortus larvae administered to guinea pigs established in the stomach and developed into fourth stage larvae. Most worms were then lost between 5 and 7 days after infection and the guinea pigs were resistant to a second infection. Haemorrhage, oedema and infiltration with inflammatory cells, especially eosinophils, developed in the stomach wall of infected guinea pigs and reactive hyperplastic changes occurred in the gastric lymph node. H. contortus infection of guinea pigs has some potential as a model for study of the pathology, immunology and chemotherapy of gastric nematodiasis.     

Opportunistic infections in hysterectomy-derived, barrier-maintained guinea pigs

Guineapigs were rederived by hysterectomy and associated with a colonization-resistant enteric microflora (CRF) of mouse origin to establish a strict barrier-maintained breeding colony. Infections were suspected in 55 of 209 animals autopsied. From 65 of 67 tissue samples selected for bacteriological examination 167 isolates, belonging to 16 usually non-pathogenic bacterial species or groups, were isolated mostly from cases of mastitis, typhlitis, enteritis, otitis media and pneumonia. Faecal streptococci, Pseudomonas aeruginosa, Clostridium perfringens, Citrobacter spp., C. freundii, Escherichia coli, Klebsiella oxytoca and Enterobacter cloacae accounted for 86.8% of all isolates. Variations in the recovery rate of these 8 species during the study and a gradual decline in the incidence of infections were observed. Elimination by rederivation of the autochthonous bacterial flora seemed to have predisposed to opportunistic infections by aerobic and facultatively anaerobic bacteria. Enteric colonization resistance to the growth of these bacteria was presumably insufficiently provided by the CRF of mouse origin and might be remedied by using a flora of guineapig origin.     

Bronchoalveolar eosinophilia in random-source versus purpose-bred dogs.

Eosinophils (EOS) have been implicated in changes in airway and vascular reactivity in a variety of disease states. Analysis of cells in bronchoalveolar lavage samples from chronic, heartworm-free random-source (RS) dogs indicated higher leukocyte counts with markedly higher percent and total numbers of EOS than were present in purpose-bred (PB) animals. Bronchoalveolar lavage fluid (BALF) obtained from RS dogs had a significantly elevated total nucleated cell count: 0.8 x 10(6) vs 0.4 x 10(6) for the PB dogs. RS dogs had 24% +/- 5% and PB dogs had 3% +/- 0.7% EOS. The RS animals with elevated EOS had similar percentages of neutrophils: 4% +/- 0.6% as the PB animals. Despite aggressive anthelminthic treatment, the abnormal BALF cellular profile of the RS animals persisted even though circulating levels of EOS in this group decreased. Analysis of BALF for thromboxane B2 (TxB2) and 6-keto-prostaglandin F1(1a) (6-keto-PGF1a) indicated that only the TxB2 levels were significantly different between groups. The RS BALF TxB2 levels were 73 +/- 14 pg/ml vs 23 +/- 3 pg/ml for the PB group (P < 0.05). Regression analysis of the relationship between increasing TxB2 levels and the absolute number of EOS per milliliter of BALF obtained from the RS dogs indicated a significant correlation (r = 0.83, P < 0.0001). No difference in plasma levels of these mediators was observed. Other physiologic parameters also differed between the two groups: the RS group had significantly increased heart rates and cardiac output under baseline conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evidence of two inapparent nonoccluded viral infections of Culex tarsalis

Culex tarsalis from a mosquito colony maintained at Bakersfield, California, were infected with two noninclusion cytoplasmic viruses. Both viruses were polyhedral with average diameters of ca. 56 nm and 33 nm for C. tarsalis virus 1 and 2 (CTV1 and CTV2), respectively. CTV1 particles had an average prevalence in the colony of 24% over a 2-year period and CTV2 had a prevalence of 5%.The viruses were first observed in negatively stained preparations of crushed heads using sodium phosphotungstate. Both viruses were seen in thin sectioned material from the salivary glands, fat body, and nervous tissue of infected mosquitoes.CTV1 was retained through six serial passages by needle inoculations of infected mosquito suspensions into virus-free C. tarsalis adults. An estimated total dilution of >;10¹⁸ indicated CTV1 had multiplied in C. tarsalis. The coincident appearance of CTV2 in some of the inoculated mosquitoes through the 5th passage suggested that this virus also multiplied on serial passage.CTV1 had a median incubation period of ca. 6.6 days in adult C. tarsalis kept at 25°C. Preliminary data indicated that the median survival period of male and female C. tarsalis injected with CTV1 was reduced 2 or 3 days over that of inoculated control insects when incubated at 25°C. Infection may cause a degeneration of salivary glands in adult females.CTV1 did not infect Culex pipiens and did not produce plaques in Vero or duck embryo cell cultures.     

Experimental cryptococcosis in guinea pigs

A guinea pig model was used to evaluate immune response to Cryptococcus neoformans. This model shared characteristics with cryptococcosis in humans. Twenty five guinea pigs injected intraperitoneally with 10(7) viable C. neoformans cells developed disseminated disease. Forty days after infection all guinea pigs were killed and autopsy performed. C. neoformans growth in the lungs, brains, livers and spleen of the infected animals were determined. Furthermore, the immune response was characterized by moderate degree of delayed-type hypersensitivity and humoral response. In some organs was observed neutrophil and lymphocyte infiltration with presence of cryptococci cells. The infiltration observed in the organs was probably a consequence of an immune reaction.     

Interstitial pneumonia in guinea pigs

Interstitial pneumonia was observed in 12 male guinea pigs. Grossly, the lung showed clear white areas in the parenchyma. Histological changes in the lung consisted of interstitial pneumonia and formation of granulomas accompanied by bacterial clumps. It was thought that this disorder might have occurred as a bacterial infection.