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.     

Experimental infection of Dirofilaria immitis in raccoon dogs

Canine heartworm (Dirofilaria immitis) is a nematode that naturally parasitizes in the pulmonary arteries and the right ventricle of domestic dogs (Canis familiaris) as final hosts. Japanese raccoon dogs (Nyctereutes procyonoides viverrinus) also are known to be susceptible to infection by the parasite. However, prevalence of this infection among free-ranging raccoon dogs is low and so is the worm burden. To examine the susceptibility of the raccoon dog to D. immitis infection, 3 raccoon dogs and 2 beagles were inoculated 4 times with 25 third-stage larvae (L3s) of D. immitis at 3-wk intervals. Worms were recovered from 2 raccoon dogs and both domestic dogs. The average percentage of recovery (2.3%) of the raccoon dogs was almost 10 times lower (24.5%) than that of the domestic dogs, but there was no significant difference in the body length of worms recovered from 2 types of hosts. To examine microfilaremia, 2 raccoon dogs were infected with 100 L3s. Microfilaremia was observed for 180 days postinoculation (PI) but disappeared at about 300 days PI. The raccoon dog was mildly susceptible to infection with D. immitis, but surviving worms developed and matured normally.     

Use of parasite antigen detection to monitor the success of drug therapy in Dirofilaria immitis-infected dogs

Recently the authors developed a monoclonal antibody-based enzyme immunoassay for circulating Dirofilaria immitis antigen and demonstrated its utility as a diagnostic tool for canine dirofilariasis. In the present study, serum parasite antigen measurements were used to monitor the success of thiacetarsamide therapy in 2 controlled trials that involved 24 naturally infected dogs. Parasite antigen levels correlated significantly with adult worm burdens in untreated control dogs. Antigen levels fell dramatically by 8 wk after treatment in successfully treated dogs and were undetectable 12 wk after treatment in dogs that were parasitologically cured. Microfilarial counts exhibited seasonal periodicity in both treated and control dogs and were not useful in monitoring the success of adulticide therapy. Parasite antigen detection is quite useful in monitoring the efficacy of adulticide therapy for dogs infected with D. immitis. This approach may lead to improved clinical use of thiacetarsamide, and it should facilitate evaluation of new drugs for this important infection.     

Canine heartworm in the domestic and wild canids of southeastern Nebraska

The prevalence of canine heartworm (Dirofilaria immitis) was examined in the domestic dog, coyote (Canis latrans), and red fox (Vulpes fulva) populations of southeastern Nebraska. Microfilariae were detected in 21.4% (22 of 103) of the domestic dogs. The average age of infection for dogs was 5.8 yr. Nine of the 22 infected dogs also were positive for Dipetalonema reconditum. Thirty-nine of 443 (8.9%) coyotes were found to have adult heartworms. The average number of male and female worms per heart was 3.7 and 3.9, respectively. The mean age of infected coyotes was 3.6 yr. Red foxes had an infection rate of 4.8% (1 of 21). This fox heart had only 1 immature female worm. A mail survey of 6 veterinary clinics was also conducted. Veterinarians reported infection rates of 0% to 18.8% in domestic dogs for their localities.     

Immunoblotting analysis of somatic components of Dirofilaria immitis

SDS-PAGE analysis of Dirofilaria immitis extracts demonstrated the complexity of somatic protein component of adult male similar to that of adult female worm. Western blot analysis showed six major peptide bands of 85, 66, 42, 20, 16.2 and 14.5 kDa recognized in the sera of infected dogs. Western blotting sera from dogs with Dirofilaria immitis infection suggest that antigenic components in the low molecular weight region may be related to the anti-parasitic mechanism of the host.     

Survey of canine heartworm in the city of Recife, Pernambuco, Brazil.

Six hundred and eleven random-source dogs (338 male, 273 female) one year of age or older, from six sections of the city of Recife, Pernambuco, were examined antemortem for circulating microfilariae Dirofilaria immitis and Dipetalonema reconditum adult heartworm (D. immitis) antigen, and examined postmortem for adult heartworms. The prevalence of heartworm infection was 2.3% (14/611), as determined by necropsy for adult worms, and 1% (6/611) had circulating microfilariae of D. immitis; thus, 57.1% of the heartworm-infected dogs had occult infections. The results of serological testing indicated that 1.3% (8/611) of the dogs were positive for adult heartworm antigen. A total of 42 (6.9%) of the dogs had microfilariae of D. reconditum; 40 of these had only D. reconditum and two additional dogs had microfilariae of both species, D. immitis and D. reconditum.     

Prevalence and Genetic Characterization of Toxoplasma gondii in Pet Dogs in Central China

The prevalence and genotype of Toxoplasma gondii infection in dogs in Henan Province, Central China was investigated. A total of 125 blood samples were collected from pet dogs during April to June 2013, and all samples were examined by indirect hemagglutination antibody test (IHA) and nested PCR. The overall T. gondii prevalence in pet dogs was 24.0% (30/125), with 20.8% (26/125) in IHA and 10.4% (13/125) in PCR, respectively. No statistical associations were found between animal gender and age and the prevalence of T. gondii infection. Thirteen positive DNA samples were genotyped using 11 PCR-RFLP markers, including SAG1, (3’+5’) SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico. Of these, only 2 samples were genotyped with complete data for all loci, and a novel genotype (type III at SAG3 and GRA6 loci, and type I at other loci) was identified. This is the first report of genetic characterization of T. gondii infection in dogs in China.     

斑氏丝虫感染Scid小鼠模型的建立

采用人工感染法,对严重联合免疫缺陷小鼠(Scid 小鼠) 进行夜现周期性斑氏丝虫实验感染研究。结果表明,斑氏丝虫经人工感染后能在Scid 小鼠体内发育成熟并产生微丝蚴,且虫体回收率较高为6～30% ,平均14-8% 。感染的10 只小鼠均在外周血中检获出微丝蚴,及解剖收集到成虫,感染成功率高达100% 。作者认为Scid 小鼠由于T、B淋巴细胞功能缺如,不能产生相应的抗丝虫感染抗体,是一种易于感染成功、潜伏期短、微丝蚴密度及成虫回收率高的较理想的实验动物。     

A new endemic focus of Gymnophalloides seoi infection on Aphae Island, Shinan-gun, Jeollanam-do

A new endemic focus of Gymnophalloides seoi infection has been discovered on Aphae Island (Shinangun, Jeollanam-do), Republic of Korea. This area, which is referred to as Bokyong-ri, is a small seashore village located in the northern portion of the island. Fecal samples were collected from a total of 57 residents and examined by the Kato-Katz and formalin-ether sedimentation techniques. Helminth eggs were detected in 37 samples (64.9%); 33 samples were positive for G. seoi eggs (57.9%), 4 for Pygidiopsis summa (7.0%), 13 for other heterophyids (22.8%), 1 for Clonorchis sinensis (1.7%), and 1 for Trichuris trichiura (1.7%). Women (70.4%) revealed higher rates of G. seoi infection than did men (46.7%), and individuals older than 50 years of age also evidenced higher rates of G. seoi infection than in other age groups (P < 0.05). In worm collection from 13 G. seoi egg positive cases, G. seoi (total 86,558 specimens), Heterophyes nocens (278), Stictodora sp. (10), Heterophyopsis continua (3), P. summa (3), and unidentified flukes (42) were collected. Oysters, the source of G. seoi infection, were collected from an area proximal to the village and 50 were examined for metacercariae; 47 (94%) were found infected and the observed metacercarial density was 9.5 +/- 8.9 per oyster. The results of this study indicate that Bokyong-ri is a new endemic area of G. seoi infection, with high rates of infection in humans and oysters.     

Development of resistance to reinfection by Clonorchis sinensis in rats

We investigated the induction of resistance to Clonorchis sinensis infection by prior infection in rat and hamster models. Animals were challenged with C. sinensis metacercariae, then treated with praziquantel and reinfected. Worm recovery rate in reinfected animals was used to estimate resistance to reinfection. The determined resistance rates to reinfection in rats and hamsters were 97.7% and 10.3%, respectively. In rats, cure from the primary infection of C. sinensis increased resistant to reinfection, and the greater the worm burden and the longer the duration of primary infection, the higher was the resistance rate. For primary infection doses of 10, 40 and 100 metacercariae per rat, the resistance rates were 87.4%, 93.8% and 98.4%, respectively. The resistance rates in rats after 2 or 8-week primary infection were 78.7% and 95.3%, respectively. All worms recovered from reinfected rats were immature. When cured rats were administered with methylprednisolone, resistance to reinfection became impaired. These findings indicate that rats develop a high degree of resistance to reinfection by C. sinensis after cure. The growths and maturations of reinfected worms were also impaired.     

Serological and molecular studies on Dirofilaria immitis in dogs from Turkey

We estimated the prevalence of Dirofilaria immitis infection in domestic dogs in five Turkish provinces - Sakarya, Kocaeli, Ankara, Elazig and Mersin - using a commercial ELISA kit for detecting circulating antigen and a PCR test for detecting circulating microfilarial DNA. A total of 211 whole-blood and serum samples were collected from dogs of various breeds, ages and life status (owned or stray). Sample population characteristics were recorded and examined for differences in prevalence. Additionally, we collected 15 blood samples from cats (14 owned and 1 stray) from Ankara province and used PCR to detect D. immitis infection. Twenty-seven (12.8%) of 211 dog samples were positive for D. immitis antigen by ELISA. No differences in prevalence were observed by sex (female: 14.4%; male: 10.7%; P>0.05). The prevalence of D. immitis infection varied with age: 11.8% in younger dogs (0.5-2 years) and 17.5% in older dogs (3-5 years). Prevalence between stray dogs (15.2%) and owned dogs (9.3%) did not differ (P>0.05). Prevalence rates were highest in Kocaeli province (18.3%), followed by Ankara (14.8%), Sakarya (12.3%) and Mersin (10.5%) provinces. Prevalence in Elazig province was 0%. No dogs or cats had microfilarial DNA detectable by PCR.     

Susceptibility of several strains of mice to Echinostoma hortense infection

Susceptibilities of 5 different mice strains, including C3H/HeN, BALB/c, C57BL6, FvB and ICR, to Echinostoma hortense infection, was evaluated. The worm expulsion rate, worm size and egg production were observed from 1 to 8 weeks after infection with 30 metacercariae. C3H/HeN and ICR mice showed the highest worm maturation rates. The worm recovery rate and the number of eggs per gram (EPG) of feces was also higher in C3H/HeN and ICR mice than in BALB/c, C57BL6, and FvB mice. It is suggested that E. hortense is highly infectious to ICR and C3H/HeN mice, but not to the other strains of mice. Based on the results obtained, we believe that the susceptibility of different mouse strains to E. hortense infection is dependent on the genetic and immunologic background of mice.     

An ivermectin-sensitive glutamate-gated chloride channel subunit from Dirofilaria immitis

Dirofilaria immitis is a filarial nematode that infects dogs and causes cardiopulmonary disease. The most effective way of controlling the infection is by chemoprophylaxis, using members of the avermectin/milbemycin (A/M) class of anthelmintics, which includes ivermectin; these drugs act at invertebrate glutamate-gated chloride channels (GluCl). We have cloned two cDNAs encoding D. immitis GluCl subunits and demonstrated that at least one may be an important molecular target for the A/Ms in vivo. The subunits are orthologues of the alternatively spliced GluClalpha3A and alpha3B subunits (encoded by the avr-14 gene) previously identified in Caenorhabditis elegans and in Haemonchus contortus. Although the alternative splicing of avr-14 is conserved across the species, the processing of the mature GluClalpha3A mRNA differs in D. immitis compared to C. elegans and H. contortus. Two-electrode voltage clamp recordings were made from Xenopus oocytes injected with subunit-specific cRNAs. The DiGluClalpha3B subunit formed channels that were gated by L-glutamate (1-100 mM) and ivermectin (1 microM). Oocytes injected with DiGluClalpha3A cRNA failed to respond to L-glutamate. The qualitative responses obtained were consistent with the pharmacology observed for the GluClalpha3 subunits from C. elegans and H. contortus.     

Persistent endemicity of Gymnophalloides seoi infection in a southwestern coastal village of Korea with special reference to its egg laying capacity in the human host

Follow-up studies have been conducted every three years on the endemicity of Gymnophalloides seoi infection in a small coastal village of Chollanam-do (Province), Korea, since it was first known as an endemic area in 1994. Special attention was given to its egg laying capacity in the human host. In fecal examinations, the overall helminth egg and/or cyst positive rate was 78.7% (74/94) in 1997 and 76.6% (82/107) in 2000. Among them G. seoi eggs showed the highest rate; 71.3% (67/94) in 1997 and 72.0% (77/107) in 2000. The average number of eggs per gram of feces (EPG) was 1,015 in 1997, while a reduced rate of 353 was observed in 2000. In 1997, total of 320,677 adult flukes of G. seoi (av. 10,344/person, 94-69,125 in range) were collected from the diarrheic stools of 31 treated patients. The EPG/worm obtained from 21 cases ranged from 0.04 to 0.77 (av. 0.23), suggesting density-dependent constraints on the worm fecundity. The relationship between the worm burden (X) and EPG/worm (Y) can be expressed as Y = 0.42.e-1.2 chi (r = 0.49). The results showed that G. seoi infection is persistently endemic in this village.     

Infection rate and genetic diversity of Giardia duodenalis in pet and stray dogs in Henan Province,China

Giardia duodenalis is an important protozoan parasite that is known to be zoonotic. To assess the potential zoonotic transmission of giardiasis from dogs and to identify genetic diversity of G. duodenalis in dog populations, we examined the infection rate and genotypes of G. duodenalis in both pet dogs (from pet dog farms, pet shops, pet hospitals, pet markets) and stray dogs of different ages in Henan Province, China. A total of 940 fresh fecal specimens were collected from 2007 to 2013 in Henan Province. The overall infection rate of G. duodenalis was 14.3% (134/940) as determined by microscopy, with the highest infection rate (17.3%) observed in dogs from shelters. Young dogs were more likely to be infected with G. duodenalis than adult dogs, and G. duodenalis cysts were found more frequently in diarrheic dogs. All G. duodenalis-positive isolates were characterized at the triose phosphate isomerase (tpi), glutamate dehydrogenase (gdh), and β-giardin (bg) loci, and 37, 51, and 48 sequences were obtained, respectively. The dog-specific assemblages C and D were identified using multi-locus sequence analysis. Six novel sequences of the tpi locus, one novel sequence of the gdh locus and two novel sequences of the bg locus were detected among the G. duodenalis assemblage C isolates, while two novel sequences of the gdh locus were found among the G. duodenalis assemblage D isolates. Our data indicate that G. duodenalis is a common parasite and cause of diarrheal disease in dogs in Henan Province. However, there was no evidence for zoonotic G. duodenalis assemblages in the study population.     

Anti-Dirofilaria immitis antibody levels before and after anthelmintic treatment of experimentally infected dogs

Antibody to Dirofilaria immitis was measured in 6 dogs before and after treatment with thiacetarsamide. Antibody to microfilarial surface antigens was ascertained with an indirect fluorescent antibody assay (IFA). Various patterns of the production, or presence, of antibody to microfilarial surface antigens were observed. There was no apparent relationship between IFA results and adulticide success. Antibody to adult worm antigen was measured with an enzyme-linked immunosorbent assay (ELISA). ELISA titers increased following infection and decreased transiently at the end of the prepatent period. A marked increase in ELISA titers was noted in all dogs subsequent to an initial thiacetarsamide treatment. In general, ELISA titers returned to low levels in dogs which were successfully treated; however, in dogs with persistent infections or infections which apparently necessitated 2 adulticide treatments ELISA titers remained at pre-treatment levels during the period of observation. Since ELISA titers appeared to decrease to pre-infection levels in successfully treated dogs, the assay should have utility in subsequent antibody determinations and may permit retrospective prediction of chemotherapeutic success.     

Echinococcus granulosus infection in dogs in Tambool, Sudan

In the Tambool area (Central eastern Sudan) a survey was made of the infection rate of Echinococcus granulosus in dogs. From the total of 49 dogs shot by the police authority, 25 (51%) had E. granulosus in their intestines. The range of worm recovery was 7 to 28,400. These high infection and recovery rates could be explained by the rate of infection in the intermediate host (camel) slaughtered in the area.     

Persistent infection with Strongyloides venezuelensis in the Mongolian gerbil (Meriones unguiculatus)

To examine the fate of Strongyloides venezuelensis. Mongolian gerbils (Meriones unguicalatus) were orally infected with 1,000 L3 larvae per animal. Altogether, 50 gerbils divided into 5 groups of 10 each were monitored for a period of 570 days to document the kinetics of faecal egg output, adults worm population, morphological development, fecundity, and hematological changes including peripheral blood eosinophilia. This study chronicled a life long parasitism of S. venezuelensis in the gerbil host, and showed that S. venezuelensis infection was quite stable throughout the course of infection and the worms maintained their normal development as evidenced by their body dimension. A progressive loss of body condition of the infected gerbils was observed as the level of infection advanced. However, no detectable pathological changes were observed in the gastrointestinal tract. The present findings indicate that an immunocompetent host, such as the Mongolian gerbil, can serve as a life long carrier model of S. venezuelensis if the worms are not expelled within 570 days after infection.     

Ancylostoma ceylanicum: immunization with soluble worm extract and responses to challenge infection of dogs

When dogs were immunized with soluble extract of adult Ancylostoma ceylanicum antigen, they were partially resistant to challenge infection in this model of human hookworm infection. Two immunizing doses, each of 1 mg protein suspended in Freund's complete adjuvant, were administered to one group of animals 1 and 3 weeks prior to infection with 5000 larvae. When compared with control dogs given the same infective dose, fecal egg excretion and intestinal adult worm burden in the immunized animals were reduced by 59 and 74%, respectively. Infection had no significant effect on hemoglobin concentrations, mean red cell volumes, total white cell counts, platelet levels, or spontaneous and phytohemagglutinin-induced lymphocyte transformations in both control and immunized animals. Both groups developed an eosinophilia, and lymphocytes from the immunized dogs responded transiently to stimulation with both larval and adult worm antigens. Specific IgM antibodies were transitory in both groups of dogs following infection. IgG antibodies developed significantly 2 weeks after infection in the immunized group; however, they did not appear until 4 weeks after infection in the control group. Both groups developed IgA antibodies 1 week after infection. They were maintained in the control dogs, in contrast to the levels in immunized animals which subsided rapidly 4 weeks after infection. Therefore, when animals are injected with soluble adult worm antigen prior to infection, specific protective immunity is acquired.