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The ultrastructural development of the macrogamete and formation of the oocyst wall of Toxoplasma gondii.

The macrogametes of Toxoplasma gondii develop within the epithelial cells of the cat ileum. As they develop the nucleus enlarges and dense patches of chromatin which were present in the nucleoplasm, disappear. Polysaccharide granules and lipid globules appear in the cytoplasm and increase in number during development. The wall-forming bodies of Type I (WFB I) appear before the wall-forming bodies of Type II (WFB II); WFB I are smaller, more osmiophilic and more numerous than the WFB II. The WFB I appear to form from vesicles produced by the smooth endoplasmic reticulum, and the WFB II form within the lacunae of the rough endoplasmic reticulum. Double membraned vacuoles appear to form from the nuclear membranes but the function of these is unknown. Throughout development the macrogamete retains a normal pellicle which possesses numerous micropores. The first evidence of oocyst wall formation is the appearance of participate matter in the parasitophorous vacuole which precipitates to form Layer 1 of the oocyst wall. Layers 2 and 3 are unit membranes which form between Layer 1 and the pellicle. During this development the organism has an organelle complement similar to that of the macrogamete. Layers 4 and 5 form between Layer 3 and the pellicle. Layer 4 is osmiophilic and its formation is accompanied by the disappearance of WFB I. Layer 5 is less osmiophilic than Layer 4 and its formation is accompanied by the disappearance of WFB II. The two innermost layers (Layers 4 & 5) in the oocyst wall of Toxoplasma are similar to those found in Isospora spp. and Eimeria spp. Toxoplasma seems to be unusual in that, firstly, it possesses an additional 3 layers and, secondly, all 5 layers are formed outside the pellicle of the original macrogamete.

Animals↗

Internal parasites of feral cats from the Tasmanian Midlands and King Island.

Eighty-six feral cats from a sheep grazing area in the Tasmanian Midlands and 21 from King Island were examined for internal parasites. Major food items in order of decreasing prevalence in stomach contents were insects, lizards, birds, rodents and frogs in the Midlands, and rodents, birds, insects, and lizards on King Island. Feral cats from the Midlands had 4 cestode, 7 nematode, 2 trematode and 3 protozoan parasites as follows: Spirometra erinacei (66.3%), Taenia taeniaeformis (2.3%), Dipylidium caninum (1.2%), Toxocara cati (86.0%), spiruroid nodules containing Cylicospirura felineus and Cyathospirura dasyuridis (57.0%), Ollulanus tricuspis (11.4%), Uncinaria stenocephala (2.3%), Aelurostrongylus abstrusus (39.2%), Capillaris aerophila (30.0%), Echinoparyphium sp (27.1%), Fibricola minor (6.8%), Isospora felis (12.7%), I. rivolta (5.4%), and Sarcocystis sp (1.8%). Antibodies to Toxoplasma gondii were found in 51 of 53 serums. Three cestode and 5 nematode parasites were found in cats from King Island: T. taeniaeformis (49.2%), D. caninum (23.8%), S. erinacei (19.0%), T. cati (90.5%), C. felineus (42.9%), C dasyuridis (9.5%), O. tricuspis (4.8%) and C. aerophila (9.5%). This is the first record of Cylicospirura felineus, Fibricola minor and Echinoparyphium sp in cats in Australia.

Animals↗

The prevalence of Dirofilaria immitis and other parasites in urban pound dogs in north-eastern Victoria.

The results of a survey investigating the prevalence of dirofilaria immitis and other helminth and protozoan infections in urban dogs in north-eastern Victoria are presented. D. immitis was detected in 2.7% of the general population (8.3% of dogs older than 2 years). Microfilariae of D. immitis were not detected in the peripheral circulation of 30% of dogs infected with the adult parasites. The most prevalent gastro-intestinal parasites were Dipylidium caninum 57%; Trichuris vulpis 41%; Toxocara canis 38%; and Uncinaria stenocephala 26%. The prevalence of T. canis in dogs less than one year of age was 73% and this decreased with increasing age. No Echinococcus granulosus adults were detected. Sarcocystis spp and isospora ohioensis were the most commonly seen coccidians.

Animals↗

Sporozoa in dogs and cats.

Faecal samples from 110 dogs and 71 cats were examined for sporozoan parasites by flotation. Isospora spp were present in 5.5% dogs and 4.2% cats; Sarcocystis spp in 20.9% dogs and 1.4% cats. 74.5% dogs and 77.5% cats were fed raw meat from various sources; beef was fed most often. Animals fed raw meat were more frequently infected with protozoa. No Toxoplasma oocysts were found. The results are compared with those from other surveys in Australia and New Zealand.

Animals↗

[Detection of intestinal parasites from dogs in Tochigi-City in 1979 and 1991].

To clarify whether sanitary and hygienic conditions surrounding humans and pet animals have improved or not, we examined feces from dogs for intestinal parasites in Tochigi in 1979 and 1991. Intestinal parasites were detected from 109 of the 262 dogs (41.9%) in 1979 and 86 of the 260 dogs (32.8%) in 1991. Among the parasites. Ancylostoma caninum, Tirchuris vulpis and Toxocara canis were most commonly detected, and their detection rates were higher in 1979. On the contrary, Dipylidium caninum, Strongyloides stercoralis, Isospora spp., which are important causes of human diseases, were detected at higher rates in 1991. In the dogs of outdoor feeding, the detection rates of parasites were markedly decreased, but slightly increased in the dogs of indoor feeding in 1991. These results suggest that sanitary conditions surrounding pet animals have not been sufficiently improved, in spite of the fact that humans are in more contact with their pet animals.

Animals↗

[The current status of infectious enteritis in Japan--reports of the "Research Group for Infectious Enteric Diseases, Japan" in the last 5 years (1996-2000)].

The patients or carriers with infectious enteritis admitted to the Hospitals for infectious diseases in the last 5 years (1996-2000) were studied. The total number of cases admitted in each year were 969, 1,113, 981, 637 and 573 respectively. A total of 1,527 Shigella spp. strains including 1,078 strains from overseas travelers' cases were isolated. The isolates of Salmonella spp. excluding S. Typhi and S. Paratyphi A were 562 in number. A total of 61 Vibrio cholerae O1 strains including 44 strains from overseas travelers was isolated. These V. cholerae O1 strains were all of El Tor type. Entamoeba histolytica, Giardia lamblia, Cryptosporidium parvum and Isospora belli were detected in 225, 46, 3 and 3 cases respectively. Abdominal pain, nausea and vomiting were frequently observed in the cases caused by Vibrio parahaemolyticus. The highest body temperature and the highest frequency of bowel movements were revealed in the cases caused by Salmonella spp. Bloody stool was observed in 55.3% of the cases due to Escherichia coli, in 40.5% of the cases due to Campylobacter spp. and in 24.1% of cases due to Shigella spp. As for shigellosis and salmonellosis, the clinical symptoms were more serious in the domestic cases than those in travelers. OFLX-resistant strains accounted for 1.7% of Shigella spp. isolates. No strains of Salmonella spp. were resistant to OFLX. The incidence of drug-resistant isolates of Campylobacter jejuni were 26.0% for OFLX and 2.5% for EM.

Drug Resistance, Bacterial↗

Toxoplasma gondii: the oocyst, sporozoite, and infection of cultured cells.

The infective form of Toxoplasma gondii fouind in cat feces is an oocyst wihich, when sporutlated, resembles that of the genus Isospora in havinig two sporocysts. Sporozoites obtained by artificial excystation of the oocyst are infective for monkey kidney cell cultures. Ultrastructural characteristics of sporozoites resemble those seen previously in proliferative stages of Toxoplasma gondii.

Animals↗

Toxoplasma gondii in cats: fecal stages identified as coccidian oocysts.

Isospora-type oocysts were excreted by cats following the ingestion of Toxoplasma fromn infected mice. Oocysts appeared 3 to 5 days after cyst. were ingested and 8 to 10 days after trophozoites were ingested, and also 21 to 24 days after the administration of infective fecal suspensions from cats. A close quanititative and biologic correlation between oocysts and Toxoplasma infectivity of the feces was observed which could not be separated by density gradient centrifugation and filtration methods. Toxoplasma is an intestinal coccidian of cats which is fecally spread. It has evolved to multiply in brain and muscle and in other species, making it possible for carnivorism to become another means of transmission.

Animals↗

HEp-2 cell-adherent Escherichia coli and intestinal secretory immune response to human immunodeficiency virus (HIV) in outpatients with HIV-associated diarrhea.

HEp-2 cell-adherent Escherichia coli and the human immunodeficiency virus (HIV) itself have recently been incriminated as causes of chronic HIV-associated diarrhea. This study sought to determine the prevalence of these two agents among HIV-infected patients with diarrhea in an outpatient setting in the United States and to compare their prevalence to that of other commonly recognized enteropathogens known to be present in this population. HEp-2 cell-adherent E. coli was found in 20 of 83 (24.1%) patients with diarrhea. A diffuse pattern of adherence was the most common, found in 14 of 20 (70%) patients, followed by a localized adherence pattern (6 of 20; 30%). An intestinal secretory immune response against the p24 antigen of HIV was found in 9 of 34 (27.5%) patients with HIV-associated diarrhea. The following pathogens or products were also detected in lower frequencies: Cryptosporidium spp. (10.8%), Clostridium difficile toxin (8.8%), microsporidia (6%), Isospora belli (3.6%), Blastocystis hominis (2.4%), Giardia spp. (1.2%), Salmonella spp. (1.2%), and Mycobacterium spp. (1.2%). The role of HEp-2 cell-adherent E. coli and HIV enteric infections in patients with HIV-associated diarrhea deserves further study.

Bacterial Adhesion↗

Demonstration of serum antibodies to Cryptosporidium sp. in normal and immunodeficient humans with confirmed infections.

Antibodies to Cryptosporidium sp. were detected in sera from 12 immunocompetent individuals recovered from cryptosporidiosis and from 5 subjects with an acquired immunodeficiency syndrome and persistent cryptosporidiosis by an indirect immunofluorescent (IIF) test. Marked seroconversion accompanied recovery from infection in immunocompetent individuals, and their IIF titers remained high (1:40 to 1:640) for at least 1 year. No antibodies to Cryptosporidium sp. were detected in sera from two subjects with hypogammaglobulinemia, normal T-cell function, and persistent cryptosporidiosis or in sera from individuals not previously exposed to Cryptosporidium sp. Very little or no cross-reactivity with the other coccidia--Toxoplasma, Sarcocystis, and Isospora spp.--occurred in the IIF test procedure. The application of this IIF procedure, along with recently developed techniques to detect oocysts in the feces, should provide the basis for a more accurate assessment of the number of individuals within any subject group with previous and active Cryptosporidium infections.

Acquired Immunodeficiency Syndrome↗

Prevalence of enteric parasites in homosexual patients attending an outpatient clinic.

A total of 372 pooled stool specimens from 274 homosexual men with diarrhea were submitted for parasitologic examination over a 2.5-year period. Each two-vial pooled specimen set contained portions of stool from 3 consecutive days in Formalin and polyvinyl alcohol. Of the 274 patients, 133 (48.5%) harbored one or more intestinal protozoa, with 161 (43.3%) of the 372 specimens submitted being positive for one or more organisms. The parasites identified included Entamoeba histolytica (71 patients), Giardia lamblia (22 patients), Endolimax nana (106 patients), Entamoeba coli (39 patients), Entamoeba hartmanni (25 patients), Dientamoeba fragilis (3 patients), Iodamoeba bütschlii (2 patients), and Chilomastix mesnili (2 patients). Cryptosporidium sp. (2 patients) and Isospora belli (1 patient) were also detected. Results of this study support the experience of other workers regarding high rates of infection with intestinal parasites in the homosexual population and also indicate that symptomatic individuals belonging to this acquired immunodeficiency syndrome risk group be screened for both common and uncommon intestinal pathogens.

Adult↗

Detection of microsporidia by indirect immunofluorescence antibody test using polyclonal and monoclonal antibodies.

During a screening for monoclonal antibodies (MAbs) to the microsporidian Encephalitozoon hellem, three murine hybridoma cell lines producing strong enzyme-linked immunosorbent assay (ELISA) reactivities were cloned twice, were designated C12, E9, and E11, and were found to secrete MAbs to the immunoglobulin M isotype. On subsequent ELISAs, the three MAbs reacted most strongly to E. hellem, and they reacted somewhat less to Encephalitozoon cuniculi and least to Nosema corneum, two other microsporidian species. The MAbs produced values of absorbance against microsporidia that were at least three times greater than reactivities obtained with control hybridoma supernatants or with uninfected host cell proteins used as antigens. By Western blot immunodetection, the three MAbs detected three E. hellem antigens with relative molecular weights (M(r)s) of 62, 60, and 52 when assayed at the highest supernatant dilutions producing reactivity. At lower dilutions, the MAbs detected additional proteins with M(r)s of 55 and 53. By using indirect immunofluorescence antibody staining, the MAbs, as well as hyperimmune polyclonal murine antisera raised against E. cuniculi and E. hellem, were able to detect formalin-fixed, tissue culture-derived E. cuniculi and E. hellem and two other human microsporidia, Enterocytozoon bieneusi and Septata intestinalis, in formalin-fixed stool and urine, respectively. E. bieneusi, however, stained more intensely with the polyclonal antisera than with the MAbs. Neither the MAbs nor the hyperimmune murine polyclonal antibodies detected Cryptosporidium, Giardia, Trichomonas, or Isospora spp. At higher concentrations, the polyclonal antisera did stain N. corneum and yeast cells. The background staining could be absorbed with Candida albicans. These results demonstrate that polyclonal antisera to E. cuniculi and E. hellem, as well as MAbs raised against E. hellem, can be used for indirect immunofluorescence antibody staining to detect several species of microsporidia known to cause opportunistic infections in AIDS patients.

AIDS-Related Opportunistic Infections↗

Myxobolus sp., another opportunistic parasite in immunosuppressed patients?

During a study of intestinal parasitic infections in human immunodeficiency virus-positive patients, a parasite belonging to the phylum Myxozoa, recently described from human samples, was identified in one sample. When this parasite was stained by the modified Ziehl-Neelsen staining method, the features of the spores were identified: they were pyriform in shape, had thick walls, and had one suture and two polar capsules, with each one having four or five coils. The suture and two polar capsules were observed with the chromotrope-modified stain. The number of stools passed was more than 30 per day, but oocysts of Isospora belli were also found. Upon reexamination of some formalin- or merthiolate-iodine-formaldehyde-preserved samples an identical parasite was found in another sample from a patient presenting with diarrhea. Strongyloides stercoralis larvae and eggs of Hymenolepis nana and Ascaris lumbricoides were also found in this sample. Given that both patients were also infected with other pathogens that cause diarrhea, the possible pathogenic role of this parasite could not be established. The probable route of infection also could not be established.

AIDS-Related Opportunistic Infections↗

Cohort study of Guinean children: incidence, pathogenicity, conferred protection, and attributable risk for enteropathogens during the first 2 years of life.

We recruited 200 children shortly after birth and collected stool specimens weekly, irrespective of whether the children had diarrhea, until up to 2 years of age. All children were recruited during the first year of the study and were monitored for a median of 18.4 months. To measure pathogenicity, the odds ratio for diarrhea, adjusted for age, sex, and coinfections with other enteropathogens, was determined by logistic regression. Standard estimation of the population attributable risk indicated that rotavirus, enterotoxigenic Escherichia coli that produced only the heat-stable toxin ST, Isospora spp., Cryptosporidium parvum, Shiga toxin (Stx)-producing E. coli (STEC), and Shigella spp. or enteroinvasive E. coli were the most important contributors to diarrhea in this population. Stx2- but not Stx1-producing STEC strains were pathogenic. Enteroaggregative E. coli, diffusely adherent E. coli, and attaching-and-effacing E. coli strains, which were the most commonly isolated microorganisms, were not associated with diarrhea. For most of the microorganisms, primary infections did not confer protection against reinfection with the same organism, but some conferred protection against diarrhea from reinfection.

Age Factors↗

Coccidian-like nature of Toxoplasma gondii.

Specific pathogen-free domestic cats were fed with tissue cysts containing Toxoplasma gondii. In two infected cats large numbers of oocysts were produced in the faeces; no oocysts were observed in the faeces of the uninfected control cat. Five days after the feeding of the toxoplasms profuse schizogonic and gametogonic stages were observed in the epithelial cells of the small intestine of one infected cat. A single schizont was observed in an intestinal epithelial cell of a second cat six days after being fed the tissue cysts. There was no evidence of schizogony or gametogony in the uninfected control cat. The stages observed in the intestinal epithelium are identical with those of the well-known endogenous cycles of coccidian parasites. The appearance of these stages, together with the nature of the oocyst, indicates that T. gondii is a coccidian parasite closely related to the genus Isospora.

Animals↗

Coccidial infection in a cat colony.

The significance of coccidiosis in the cat is discussed and the clinical signs of infection are described. The occurrence of subclinical infection with Isospora felis in 49 of 58 cats in a colony is reported. Treatment with a 20% solution of sulphadimethoxine at a dose rate of 50 mg per kg bodyweight, administered in the food daily for 14 days, was successful in eradicating the infection. Sulphadimidine appeared to have no effect on the number of oocysts in the faeces of one cat. Ancillary hygienic measures included the use of disposable feeding and drinking utensils, frequent removal and destruction of faeces and scrubbing of sanitary trays and cages with hot 5% sodium carbonate solution.

Animals↗

Prevalence of intestinal parasites in domestic cats from the London area.

The prevalence of intestinal parasites in domestic cats from the London area was surveyed over an 18-month period by microscopic examination of faecal samples. Of the 947 cats examined 11.5 per cent were infected with Toxocara cati, 1.9 per cent with Isospora felis, 1.2 per cent with Dipylidium caninum, 1.2 per cent with Taenia taeniaeformis, 0.8 per cent with I rivolta and 0.2 per cent with Toxascaris leonina.

Animals↗

Field study of coccidial and rotaviral diarrhoea in unweaned piglets.

A study of diarrhoea in unweaned piglets was carried out in nine herds, with special reference to the enteropathogenic agents which could be demonstrated. Coccidial (Isospora suis) and rotaviral infections were both identified, either singly or in combination. More extensive studies of I suis infection were undertaken in two of the herds and it was found that diarrhoea occurred most commonly in five- to 14-day-old piglets. Piglets with I suis infection were not necessarily diarrhoeic but grew poorly compared to uninfected piglets. I suis infection in litters correlated with oocyst excretion in sows. In herds with I suis infection, amprolium and monensin were used in the sow ration to achieve control, and in one herd oral dosing of piglets with amprolium in the first three or four days of life was carried out.

Animals↗