Toxocara canis: impact of preweaning nutritional deprivation on the pathogenesis of pneumonia in the mouse

The present study was conducted to better understand the immure response to Toxocara canis pneumonia in mice with preweaning nutritional deprivation. Breast-fed Swiss mice, undernourished due to large litter size (up to 15 pups) and paired controls with only 5-8 pups were used. At 21 days old, both groups were infected with T. canis larvae. Liver retinol, retinyl palmitate, and inflammatory infiltrate in lungs were compared in both groups. Significantly lower levels of retinol and retinyl palmitate in liver tissue confirmed the hypovitaminosis A (P < 0.0001 for both comparisons) in the nutritionally deprived animals. Histological analysis showed similar eosinophilic infiltration in both groups at day 3 but was significantly more severe in undernourished mice at day 20 post-infection (P = 0.01). The present findings indicate that preweaning undernourishment is associated with a more severe inflammation in response to T. canis pneumonia. It suggests that vitamin A deficiency that persists after nutritional rehabilitation, may contribute to the severity of T. canis infection. The authors suggest that nutritional status should be carefully investigated in patients with more severe clinical findings.     

Prolactin evokes lactational transmission of larvae in mice infected with Toxocara canis

We investigated the trans-lactational maternal–neonatal transmission of Toxocara canis larvae in mice, with particular interest in the role of prolactin in their migration to the mammary gland. Two female mice were infected with 300 T. canis eggs soon after delivery of 27 offspring. After 1 week of breast-feeding, seven larvae were recovered from 4 of 13 offspring. After 2 weeks of lactation, 101 larvae were recovered from all the remaining offspring. Daily prolactin administration (5 μg) was performed 2 weeks before T. canis infection and continued until 2 weeks after infection in six non-pregnant female mice, which resulted in larval accumulation in the mammary gland. Furthermore, prolactin administration in female mice that had been infected with T. canis 4 weeks prior to prolactin treatment induced migration of larvae into the mammary gland. These findings suggest that prolactin is a promoting factor contributing to lactational transmission of T. canis larvae in mice.     

Effects of Toxoplasma gondii and Toxocara canis Antigens on WEHI-164 Fibrosarcoma Growth in a Mouse Model

Cancer is the main cause of death in developed countries. However, in underdeveloped countries infections and parasitic diseases are the main causes of death. There are raising scientific evidences indicating that parasitic infections induce antitumor activity against certain types of cancers. In this study, the effects of Toxoplasma gondii and Toxocara canis egg antigens in comparison with Bacillus Calmette Guerin (BCG) (known to have anticancer distinctive) on WEHI-164 fibosarcoma transplanted to BALB/c mice was investigated. Groups of 6 male BALB/c mice injected with T. gondii antigen, BCG, or T. canis egg antigen as case groups and alum alone as control groups. All mice were then challenged with WEHI-164 fibrosarcoma cells. The mice were examined for growth of the solid tumor and the tumor sizes were measured every other day up to 4 wk. The mean tumor area in T. gondii, BCG, or alum alone injected mice in 4 different days of measurements was 25 mm², 23 mm², and 186 mm² respectively. Also the mean tumor area in T. canis injected mice in 4 different days was 25.5 mm² compared to the control group (alum treated) which was 155 mm². T. gondii parasites and T. canis egg antigens induced inhibition of the tumor growth in the fibrosarcoma mouse model. We need further study to clarify the mechanisms of anti-cancer effects.     

Serodiagnosis of Toxocariasis by ELISA Using Crude Antigen of Toxocara canis Larvae

Toxocariasis is a worldwide zoonosis caused by larvae of ascarid nematodes of dogs or cats, Toxocara canis or T. cati. Diagnosis of human toxocariasis currently relies on serology that uses T. canis excretory-secretory antigen to detect specific IgG antibodies by ELISA. We investigated the serodiagnostic efficacy of ELISA using crude antigen of T. canis larvae (TCLA). Serum specimens of 64 clinically confirmed toxocariasis, 115 healthy controls, and 119 other tissue-invading helminthiases were screened by ELISA using TCLA. The ELISA using TCLA showed 92.2% (59/64 patient samples) sensitivity and 86.6% (103/119) specificity. Its positive diagnostic predictivity was 78.7% and negative predictivity was 97.8%. No serum of healthy controls reacted but that of anisakiasis (45.5%), gnathostomiasis (19.2%), clonorchiasis (15.8%), sparganosis (11.1%), and cysticercosis (6.3%) cross-reacted. Immunoblot analysis on TCLA recognized antigenic proteins of 28- and 30-kDa bands in their dominant protein quantity and strong blotting reactivity. The present results indicate that the ELISA using our TCLA antigen is acceptable by the sensitivity and specificity for serodiagnosis of human toxocariasis. ELISA with TCLA is recommended to make differential diagnosis for patients with any sign of organ infiltration and eosinophilia.     

Transmission of Toxocara canis via ingestion of raw cow liver: a cross-sectional study in healthy adults

The aim of this study is to ascertain the relationship between ingestion of raw cow liver and Toxocara canis infection. A total of 150 apparently healthy adults were divided into 2 groups; 1 group consisted of 86 adults with positive results of Toxocara ELISA, and the other group of 64 adults with negative results. One researcher collected the history of ingestion of raw cow liver within 1 year and recent history of keeping dogs. Among 86 seropositive adults for T. canis, 68 (79.1%) had a recent history of ingestion of raw cow liver. Multivariate statistical analysis showed that a recent ingestion of raw cow liver and keeping dogs were related to an increased risk of toxocariasis (odds ratios, 4.4 and 3.7; and 95% confidence intervals, 1.9-10.2 and 1.2-11.6, respectively). A recent history of ingestion of raw cow liver and keeping dogs was significantly associated with toxocariasis.     

Cross-reactivity between sera from dogs experimentally infected with Dirofilaria immitis and crude extract of Toxocara canis

This study was performed to investigate whethere there is cross-reactivity between Dirofilaria immitis and three intestinal nematodes of dogs. In ELISA, D. immitis-infected dog sera obtained at the 4th molting stage (9-11 weeks) and microfilaremic stage (25-30 weeks) were shown to be highly reactive with crude extract of T. canis. In immunoblotting, some antigenic fractions, 44, 57, 88, 100 kDa of crude extract of T. canis, were found to be positive reaction with sera of dogs infected with D. immitis. However, little or no cross-reaction were observed between sera of D. immitis-infected dogs and crude extract antigen of T. vulpis or A. caninum. These result suggest that there are partial cross reaction between sera of D. immitis-infected dogs and the antigen of T. canis.     

An improved method to obtain antigen-excreting Toxocara canis larvae

Toxocara canis is a dog helminth which causes visceral larva migrans (VLM) when infecting humans as a larva. The infection is demonstrated by detecting IgG antibodies against excretory-secretory larval antigens (ESLA) in serum by ELISA. The production of ESLA involves the collection of adult worms from dog puppy stools, the separation of eggs from dissected uteri, and the in vitro growing of egg-derived larvae, following the time-consuming and laborious protocol described by De Savigny [De Savigny, D.H., 1975. In vitro maintenance of T. canis larvae and a simple method for the production of Toxocara ES antigen for the uses in serodiagnostic tests for visceral larva migrans. Journal of Parasitology 61, 781-782]. In this work, an improved protocol for obtaining T. canis larvae is described. The modifications proposed improved the efficiency of the original De Savigny method in three ways: (i) increasing the parasite yield up to five fold, (ii) improving the larval purity, and (iii) markedly reducing the execution time of the protocol.     

Immunopathological Changes in the Brain of Immunosuppressed Mice Experimentally Infected with Toxocara canis

Toxocariasis is a soil-transmitted helminthozoonosis due to infection of humans by larvae of Toxocara canis. The disease could produce cognitive and behavioral disturbances especially in children. Meanwhile, in our modern era, the incidence of immunosuppression has been progressively increasing due to increased incidence of malignancy as well as increased use of immunosuppressive agents. The present study aimed at comparing some of the pathological and immunological alterations in the brain of normal and immunosuppressed mice experimentally infected with T. canis. Therefore, 180 Swiss albino mice were divided into 4 groups including normal (control) group, immunocompetent T. canis-infected group, immunosuppressed group (control), and immunosuppressed infected group. Infected mice were subjected to larval counts in the brain, and the brains from all mice were assessed for histopathological changes, astrogliosis, and IL-5 mRNA expression levels in brain tissues. The results showed that under immunosuppression, there were significant increase in brain larval counts, significant enhancement of reactive gliosis, and significant reduction in IL-5 mRNA expression. All these changes were maximal in the chronic stage of infection. In conclusion, the immunopathological alterations in the brains of infected animals were progressive over time, and were exaggerated under the effect of immunosuppression as did the intensity of cerebral infection.     

Prevalence of Toxocara canis, Toxascaris leonina and Dirofilaria immitis in dogs in Chuncheon, Korea (2004)

The intestines and hearts of dogs were examined for Toxocara canis, Toxascaris leonina, and Dirofilaria immitis, after necropsy between June 26 and September 29, 2004 in Chuncheon, Korea. Of the 662 dogs examined, 6 were infected with T. canis (0.9%), 86 with T. leonina (13.0%). Fifty dogs were infected with D. immitis among 500 dogs examined (10.0%). Five were co-infected with T. canis and T. leonina, and three were co-infected with T. leonina and D. immitis. The cumulative positive infection rate for three species was 134/662 (20.2%). Considering previously reported seropositive rates of T. canis excretory-secretory antigen, i.e., 5% in the adult population in Korea, the possibility of toxocariasis caused by T. leonina should be reevaluated.     

Toxocara canis: Potential activity of natural products against second-stage larvae in vitro and in vivo

The anthelmintic activity of extracts from Chenopodiumambrosioides, Pycnanthusangolensis and Nutridesintox® was in vitro and in vivo investigated, against Toxocaracanis larvae. The in vitro assays results showed that the aqueous extract of Nutridesintox® was the most effective, followed by C. ambrosioides extracts, hexane, dichloromethane and the infusion. P. angolensis extracts showed a lower anthelmintic activity compared to the other natural products. For the in vivo assays, Nutridesintox®, the hexane extract and the infusion of C. ambrosioides were administered orally to T. canis-infected mice, in single doses, during three consecutive days. The efficacy was evaluated on the 17th day post-infection, not only by counting T. canis larvae in the tissues but also by ELISA detection of IgM and IgG antibodies and histological analysis of liver and lungs. The different treatments did not reduce the larvae burden and had no influence on the antibodies dynamic. Interestingly, a reduction on the inflammatory infiltrates was observed in the liver and lung sections of the group treated with the hexane extract of C. ambrosioides. In conclusion, the hexane extract of C. ambrosioides is of further research interest, as it showed an anthelmintic activity in vitro and a reduction on the inflammatory reaction produced by the infection of T. canis larvae in vivo.     

Fluconazole downregulates metallothionein expression and increases copper cytotoxicity in Microsporum canis

Azole antifungals are widely used to treat infections with dermatophyte fungi. Whereas it is well established that this class of drugs interferes with fungal ergosterol synthesis, little is known about its potential other biological effects. Here we report the isolation and structural organization of Microsporum canis metallothionein gene and demonstrate that fluconazole is able to downregulate the baseline as well as copper-induced expression of this gene. Since this effect occurred within 30 min after exposure of the fungus to fluconazole, it is unlikely that it is due to impaired ergosterol synthesis. Our additional demonstration that fluconazole enhances copper toxicity for M. canis suggests that inhibition of metallothionein expression by fluconazole is biologically relevant and may represent an important additional mode of the antifungal action of this drug. Therefore our data indicate that antifungal effects of azole derivatives might not only be due to interference with cell wall synthesis but may also affect other biological circuits within the fungal cells.     

Longevity of Toxocara cati Larvae and Pathology in Tissues of Experimentally Infected Chickens

This study was conducted to determine the distribution patterns and duration of stay of Toxocara cati larvae in organs of chickens and to investigate chronic phase and potential zoonotic risk of toxocariasis in chickens. Chickens were orally infected with 1,000 embryonated T. cati eggs and necropsied 240 days post-infection. Organs of the chickens were examined at gross and microscopic levels; tissues were digested to recover larvae. Peribronchiolitis with infiltration of lymphocytes, and hyperplasia of bronchiolar associated lymphatic tissues (BALT) and goblet cells, were evident in the lungs of infected chickens. There were mild hemorrhages and infiltration of lymphocytes and a few eosinophils in the meninges. Larvae were recovered from 30% of the exposed chickens. Larvae recovery indicated that T. cati larvae stay alive for at least 240 days in the chicken brain. Therefore, chickens may potentially act as a paratenic host in nature and transfer T. cati larvae to other hosts.     

Recent advances in the search for new anti-coccidial drugs

Coccidia provide a rich hunting ground for drug-designers, as there are significant biochemical differences between the parasites and their hosts. Recent years have brought the discovery of the plastid and its possible metabolic machinery, characterisation of acidocalcisomes, reports on the apparent absence from some coccidia of a typical mitochondrion, and the discovery of the mannitol cycle and shikimate pathway in the parasites. Moreover, modern technologies such as genomics and proteomics are bringing new insights into the biochemistry of coccidia and highlighting possible drug targets in abundance. A major issue for would-be drug discoverers is to decide upon the targets to prioritise. This review provides an update on recent findings on how coccidia differ biochemically from vertebrates. It includes discoveries within coccidian parasites themselves but also uses findings in Plasmodium to provide an overview of biochemical features that may be characteristics of many apicomplexan parasites and so potential targets for broad-spectrum drugs.     

Experimental Toxocara cati infection in gerbils and rats

Mongolian gerbils and Wistar rats were inoculated orally with 240 and 2,500 Toxocara cati embryonated eggs, respectively, to evaluate the larval recovery in different tissues and organs, such as the liver, lungs, heart, kidney, and skeletal muscles after 5, 30, 49, 70, and 92 days post-infection (PI). Larval recovery rates were 1.7-30.0% in Mongolian gerbils on days 5-92 PI and 0.2-3.8% in rats on the same days. These results indicate that Mongolian gerbils and Wistar rats are suitable experimental paratenic hosts for the study of neurological toxocariasis as well as visceral toxocariasis.     

Pyrrhocoricin as a potential drug delivery vehicle for Cryptosporidium parvum

This study analysed the intracellular delivery capacity of insect derived pyrrhocoricin with a peptide cargo in Cryptosporidium parvum in vitro using fluorescence microscopy. Results revealed that pyrrhocoricin was capable of acting as a delivery vehicle in transducing peptides across the parasite cell membrane for multiple life-cycle stages. The successful transduction may aid in target validation and the delivery of future peptide-based drugs against this important human pathogen.