Biological interaction between soil fungi and Toxocara canis eggs.

Fungi from the soil of public areas in La Plata, Argentina were isolated and evaluated for their biological interaction with Toxocara canis eggs in vitro. We isolated and identified two fungal species: Fusarium pallidoroseum and Mucor hiemalis. Each species was co-cultured with T. canis eggs in sterile distilled water. The samples were observed by light and scanning electron microscopy (SEM) at days 4, 7 and 14 post-inoculation. Under the conditions of our experiments, F. pallidoroseum exhibited a high ovicidal activity on T. canis eggs, whereas M. hiemalis exhibited no such effects.     

Contamination of dog hair with eggs of Toxocara canis

Toxocara canis, the common intestinal nematode of dogs and foxes, is the parasite responsible for human toxocarosis. It has recently been shown that dogs may harbour eggs of the parasite in their fur. To further investigate this claim a population of 100 stray dogs was examined to establish the prevalence and intensity of adult toxocaral worm infection in the intestines and eggs harboured in the hair. A novel method of washing the eggs from the hair was used. Sixty-seven percent of dogs were found to have T. canis eggs on their hair with a mean egg retrieval of nearly 584 eggs per gram from positive dogs. The age of the dog was found to be the only significant factor to influence the prevalence and intensity of eggs, with 95% of all the eggs recovered found on puppies. Thirty-nine percent of dogs were found to have adult T. canis worms in their intestine, although a significantly higher percentage of puppies (80%) were infected with worms than adults (22.5%). Puppies also had more worms per infection than adults and have a strong positive correlation between egg and worms numbers whereas adults did not. These studies show that stray dogs, particularly puppies, potentially harbour considerable numbers of eggs on their hair, at densities far higher than those reported in the soil or the general environment.     

Parasitism of Toxocara canis larvae in Japanese quails by inoculation of the ascarid eggs.

The distribution of T. canis larvae and pathological changes caused by them were studied in Japanese quails orally inoculated with 1,500, 4,000 or 15,000 embryonated eggs. Larvae were distributed mainly in the liver and, to lesser extent, in the muscles, brain, eyes and other organs. The number of larvae varied from 7 to 3,346, and from 1 to 288 in the liver and muscles (breast and legs), respectively. A small number of larvae were also recovered from the heart, gizzard, brain and eyes. In the groups of quails inoculated with 4,000 or 15,000 eggs, small white foci were observed on the surface of the liver 6 or 12 hr after inoculation. Histopathological examinations revealed necrotic lesions, leukocytic infiltration, granuloma and nodular lesions. The pathological changes became more serious with the large size of inoculum and days after inoculation.     

Renal involvement in mice experimentally infected with Toxocara canis embryonated eggs.

Histological examination of kidneys from mice experimentally infected with Toxocara canis embryonated eggs demonstrated the presence of a segmental or diffuse mesangioproliferative glomerulonephritis. Immunohistochemical studies established that renal alterations were associated with glomerular deposits of IgG, IgM and third component of complement (C3). These findings suggest that an immunomediated mechanism might possibly be involved in the genesis of kidney damage observed in mice infected with T. canis embryonated eggs.     

Combined scanning electron and light microscopy of biopsy samples of bovine uterus.

Uterine biopsies from normal cyclic cows were optimally prepared for examination in a scanning electron microscope. After examination in the scanning electron microscope the same tissues were routinely processed for paraffin sectioning and reexamined with the light microscope. Results indicate that the scanning electron microscope is satisfactory for examination of the fine surface structure of the endometrium and the light microscope for subsurface structures of the bovine uterus.     

Infectivity and pathogenicity of 14-month-cultured embryonated eggs of Toxocara canis in mice

Infectivity and pathogenicity to mice of embryonated eggs of Toxocara canis, that had been maintained in 2% formalin for 14 months at 4 degrees C, were evaluated by immunological and pathological assessment at 1, 4, 8, 12, 16, 20, 24, 28, 42 and 67 weeks post-infection (WPI). On each date, three infected mice and two age-matched uninfected mice were sacrificed for serum collection and histological processing of the liver, lungs, musculature, and brain. Infectivity assessment by enzyme-linked immunosorbent assay (ELISA) revealed that the overall immunological pattern of infected mice tended to be towards the Th2 type response. Serum IgG1 antibody titers in infected mice were significantly higher than that of the uninfected control mice throughout the trial (P<0.05). On the other hand, no significant difference in titers of IgG3 antibody, an indicator for the Th1 type response, was observed between the infected and control mice, except at eight WPI (P<0.05). Pathogenicity was assessed semiquantitatively by comparing the mean number or diameter of inflammatory foci as well as histopathological changes in the liver, musculature, brain, or lungs of the infected mice and the control mice. Each hematoxylin and eosin (H&E) stained tissue section slide was examined under 100x magnification and 15 random fields were counted. Degree of inflammatory injury among the four organs was scored and categorized into four levels: normal (0), mild (1+), moderate (2+), and severe (3+). An index of inflammatory injury (mean score of experimental group/mean score of 10 control groups of 20 uninfected mice) of 2-3 is considered as moderate to severe, 1-2 as mild to moderate, and 0-1 as normal to mild. Histopathological changes were moderate to severe in the liver and lungs, mild to moderate in the musculature, and only normal to mild in the brain throughout the trial. It is noteworthy that apocrine-like change in epithelial cells of the bile duct was observed in most of the infected mice from eight WPI onward. Furthermore, larvae trapped by organized granulomas were found in soft tissue near the musculature at 12, 20, and 28 WPI. Altogether, not only were the infectivity and pathogenicity of the 14-month-cultured T. canis embryonated eggs retained, the hatched larvae were also capable of eliciting some special pathological changes in the murine host.     

Risk of Toxocara canis eggs in stray and domestic dog hair in Egypt

The aim of the study was to assess whether the hair of stray and domestic dogs in Egypt was contaminated with the eggs of the zoonotic parasite Toxocara canis, and also to identify risk factors for T. canis for contamination. Paired samples of hair and feces were collected from 53 stray and 47 domestic dogs, and hair samples were obtained from a further 11 stray and 9 domestic dogs. All samples were examined to identify T. canis eggs and, if eggs were found, their maturation stage. Eggs were identified in 26.6% of stray and 10.7% of domestic dog's hair samples. A significantly increased risk of embryonated T. canis eggs in hair samples was found in stray dogs (p=0.04), stray dogs had 3.18 (95% CI: 1.04-9.74) times the odds of having T. canis eggs present compared with domestic dogs. There was also a significant difference (p=0.02) between the mean quantity of eggs per gram in stray (77.6±6.54) and domestic (48.7±6.65) dog's hair. Fecal examination found a T. canis egg prevalence of 35.8% and 21.3% in stray and domestic dogs, respectively. As no domestic dogs which were positive from hair samples had negative fecal samples, this indicates that the presence of T. canis eggs in hair is probably due to self contamination. Two stray dogs had positive hair samples but negative fecal samples indicating that contamination may also be environmental. As both non-embryonated and embryonated T. canis eggs were found in the hair of domestic dogs, direct contact with dogs may be a potential risk factor for transmission of T. canis eggs to humans.     

A method for locating individual leukocytes for comparative study by light and scanning electron microscopy.

A method is presented for locating individual leukocytes and platelets in Wright's stained blood films for comparative study by light and scanning electron microscopy. The individual cells in the blood films were photographed and the field was circled with a diamond marker objective. The slide was scored and broken; pieces of the stained slide containing the numbered circles were fixed (with conductive cement) to a metal stub, air dried, and coated with metallic gold. The metal stub was placed in a scanning electron microscope, and the marked cells were readily located and photographed so that their three-dimensional surface morphology could be compared with the morphologic features of stained cells in the blood film photographed with the light microscope. Characteristics of individual cell types are discussed.     

Visualization of immunosorption by scanning electron microscopy

Immunosorption has become a very important biochemical and serological tool and it is the purpose of this paper to visualize this process qualitatively using the scanning electron microscope. Different carriers (i.e. CNBr activated cellulose and Sepharose, glutaraldehyde treated acrylamide-agarose beads Magnogel, and polystyrene cover slips) were coated with different antibodies and incubated with their homologous antigens such as pneumococci, ferritin, polymeric Salmonella flagellin and mechanically detached flagella, as well as tetanus toxoid, E. coli bacteriophage T4 and Rota virus particles. As negative controls the sorbents were incubated with heterologous antigens.     

Quantitative comparison of various methods for detecting eggs of Toxocara canis in samples of sand

Six techniques for recovering unembryonated Toxocara canis eggs from sand samples were tested for efficiency and suitability for routine use. The tests were done under standardised conditions on 50g of sand samples contaminated experimentally with 10, 100 and 500 eggs of T. canis. Best result was achieved by the method of Dunsmore et al. [Dunsmore, J.D., Thompson, R.C.A., Bates, I.A., 1984. Vet. Parasitol. 16, 303-311]. The results were expressed as the number of T. canis eggs recorded and percentage rates of recovery in sand samples.     

Quantitative comparison of different methods for the detection of Toxocara canis eggs in sand samples

Eleven techniques for recovering helminth eggs from sand and soil samples were tested for efficiency and suitability for routine use. The tests were done under standardized conditions on sand samples of 100 g contaminated experimentally with 10, 100 or 1,000 eggs of Toxocara canis. Best results were achieved by a flotation-sedimentation technique (Stoye and Horn, 1986) and by a sieving method (K?hler et al., 1980), showing mean recovery rates of 43.1% and 41.4%, respectively. All other methods tested, mean recovery rates were about 20% or less.     

Environmental contamination by eggs of Toxocara species

A study was conducted to determine the level of contamination with Toxocara spp. eggs in parks and playgrounds in several central Illinois communities. A total of 135 composite 50-g soil samples were collected from 23 parks and public places in three cities in central Illinois. Of these soil samples, 22 (16.3%) contained from one to thirteen Toxocara spp. eggs. A total of 40 fecal samples were collected from the same parks. Toxocara spp. eggs were found in two (5%) of the samples.     

Morphological study of the lingual papillae in the fruit bat (Rousettus amplexicaudatus) by scanning electron microscopy and light microscopy

This study was carried on the tongues of ten normal, healthy and adult fruit bats (Rousettus amplexicaudatus, also known as the nyap biasa bat) in Yogyakarta, Java Island, Indonesia. The tongue was protrusible, elongated and flat with a rounded apex, and its width and thickness increased gradually towards to lingual root. There were two main types of lingual papillae, mechanical (filiform) and gustatory (fungiform and circumvallate). The tongue was divided into three parts (apex, corpus and radix), and then, each part was subdivided into three regions (two lateral regions and a median region). There were six subtypes of the filiform papillae—three types on the anterior part (small, scale-like and giant), one type on the middle part (leaf-like papillae) and two types on the posterior part (rosette-shaped filiform and conical filiform papillae)—in addition to transitional papillae presented on the corpus and radix. Two types of gustatory papillae were represented by a small number of fungiform papillae that are scattered among the filiform papillae on the lingual apex and corpus, while three circumvallate papillae on the posterior part are arranged in a “V” shape pointing directly at the larynx.