Advances in diagnostic approaches to Fasciola infection in animals and humans: An overviews

Fasciolosis, caused by Fasciola hepatica and F. gigantica, is an impediment to the livestock industry’s expansion and has a massively negative socio-economic impact due to its widespread prevalence in livestock. It is a waterborne zoonosis affecting human populations in the countries where rural economies are associated with livestock rearing. Conventional diagnosis of Fasciola infection is done by detecting parasite eggs in the faeces of infected animals or by immunological methods. Accurate and quick immunodiagnosis of Fasciola infection in animals and humans is based on the detection of antibodies and specific antigens expressed in the prepatent stage of the parasite. Both molecular and serodiagnostic tests developed thus far have enhanced the reliability of Fasciola diagnosis in both man and animals but are not widely available in resource-poor nations. A pen-side diagnostic test based on a lateral flow assay or a DNA test like loop-mediated isothermal amplification (LAMP) would be simple, fast, and cost-effective, enabling clinicians to treat animals in a targeted manner and avoid the development of drug resistance to the limited flukicides. This review focuses on the recent advances made in the diagnosis of this parasite infection in animals and humans.

Superoxide dismutase inhibits cytotoxic killing of Fasciola gigantica newly excysted juveniles expressed by sheep invitro

Fasciola gigantica faces a series of threats from various free radicals produced by the host immune system during its invasion through the abdominal cavity and establishment in the bile duct of ruminants, limiting the fluke viability. The role of the superoxide radical produced by Muzaffarnagari sheep immune effector cells against F. gigantica newly excysted juveniles (NEJs) is highlighted in this study, as is the critical role of superoxide dismutase enzyme (SOD) in dismutation of superoxide radicals derived from host immune effector cells in vitro. Three concentrations of the ovine immune effector cells viz. 2.5, 5, and 10 × 10⁶ cells were tested for their ability to induced cytotoxic killing of the parasite. All the three cell concentrations caused significant (p < 0.01) cytotoxic killing of NEJs in comparison to the control groups. Also, reduction of the immune effector cell concentration directly correlates with the NEJs killing. Attachment of immune effector cells to the parasite tegument in the presence of anti-F. gigantica antibodies was found to be critical in inducing NEJs killing via antibody-dependent cell-mediated cytotoxicity (ADCC). However, the addition of SOD greatly inhibits cytotoxic killing of NEJs, demonstrating the importance of SOD enzyme in fluke survival and parasite evasion of the host immunity. Thus, F. gigantica SOD warrants a promising candidate for immunoprophylactic studies in ruminants against the tropical liver fluke.

Molecular and serological detection of Anaplasma infection in carrier cattle in north India

Anaplasma marginale infection in cattle (n = 216) in the states of Uttar Pradesh and Uttarakhand, North India was screened by microscopy and nested-polymerase chain reaction (PCR). Two recombinant proteins viz. major surface protein (MSP) 5 and MSP2 of A. marginale were expressed in Escherichia coli and their potential in the detection of antibodies to Anaplasma species in the cattle was evaluated by immunoglobulin G-enzyme linked immunosorbent assay (IgG-ELISA). The MSP5 IgG ELISA results were compared with competitive (c) inhibition ELISA. Microscopy being the least sensitive diagnostic test detected 12.0% of animals positive for A. marginale infection while nested-PCR detected 87.9% of these animals as positive for A. marginale infection. The recombinant MSP5 antigen showed positive reactivity in 170/190 nested-PCR confirmed positive animals (sensitivity 89.5%) with specificity of 77.0%. In comparison, the recombinant MSP2 antigen showed lesser sensitivity and specificity of 79.0% and 69.2%, respectively. The cELISA was more sensitive and specific than IgG-ELISA. However, molecular detection by msp5 nested-PCR was highly sensitive and reliable for detection of carrier cattle for Anaplasma infection. The study indicated that a large cattle population (87.9%) was carrier for A. marginale infection in this region of the country.

Sero-detection of Toxocara canis infection in human with T.canis recombinant arginine kinase, cathepsin L-1 and TES-26 antigens

Three recombinant antigens viz. arginine kinase, cathepsin L-1 and TES-26 of Toxocara canis were expressed in Escherichia coli and evaluated for their potential in the detection of T. canis larval infection in human in immunoglobulin G-enzyme linked immunosorbent assay (IgG-ELISA). Results of the IgG-ELISA with the above recombinant antigens were confirmed with commercially available IgG detection kit for T. canis infection used as a standard test. All three recombinant antigens were 100% sensitive in the detection of positive cases (n = 6) of T. canis infection in human and were screened for their cross-reactivity in human patients with history of Toxoplasma gondii, Plasmodium vivax, Entamoeba histolytica, hydatid and hookworm infections. The recombinant TES-26 antigen showed higher specificity and cross-reacted with T. gondii infection sera only. However, arginine kinase and cathepsin L-1 recombinant antigens showed cross-reactions with sera of patients infected with T. gondii, P. vivax and E. histolytica but not with the patient sera infected with hydatid and hookworm. These results show that recombinant TES-26 is a potential diagnostic candidate antigen for human toxocarosis caused by migrating T. canis larvae.

Molecular identification of Mecistocirrus digitatus and Toxocara vitulorum in the mithun (Bos frontalis) from north-east India

Mecistocirrus digitatus and Toxocara vitulorum are common pathogenic nematode parasites of mithun (Bos frontalis). Species identification by morphological features was confirmed by molecular identification of M. digitatus and T. vitulorum. The internal transcribed spacer-2 (ITS-2) region and beta tubulin gene of M. digitatus were polymerase chain reaction (PCR) amplified and sequenced. ITS-2 sequence analysis showed 100% homology with other isolates of M. digitatus and 83% identity with Haemonchus contortus and H. placei, respectively. Likewise, ITS-1 and ITS-2 sequences of T. vitulorum were PCR amplified and sequenced. Sequence analysis of these internal transcribed spacers from five worms of the parasite from mithun showed no intraspecific variations with T. vitulorum isolates from domestic ruminants.

Pimply gut condition in mithun (Bos frontalis) calves

The present observation was recorded at National Research Centre on Mithun, Jharnapani from May 2010 to September 2012. A total of 15 mithun calves, which died in and around Jharnapani, were attended and detailed post-mortem examination was carried out. Out of these, five calves (33.33 %) aging between 1 and 1.5 years exhibiting the condition of chronic wasting and diarrhoea were found positive for pimply gut condition based on gross and microscopic examination. Post-mortem examination revealed extensive nodule formation on the wall of the rectum; however, the entire lumen did not reveal any of adult parasites. In all the cases, there were congestion in the mucous layer and thickening of the intestinal wall. Histopathological examination revealed chronic enteritis with mononuclear cell infiltration comprising mostly of macrophages, lymphocytes and eosinophils. In the muscularis mucosae, encysted larvae were found along with fibrous tissue proliferation. These lesions gave the intestine a nodular appearance as they thickened the wall and projected from the serosal surface. These extensive numbers of nodules in the intestine might have interfered with peristalsis and intestinal absorption which led to chronic wasting and diarrhoea in the calves.

Molecular detection and genetic diversity of Babesia gibsoni in dogs in India

Babesia gibsoni is a tick borne intraerythrocytic protozoan parasite causing piroplasmosis in dogs and has been predominantly reported in Asian countries, including Japan, Korea, Taiwan, Malaysia, Bangladesh and India. The present communication is the first evidence on the genetic diversity of B. gibsoni of dogs in India. Blood samples were collected from 164 dogs in north and northeast states of India and 13 dogs (7.9%) were found positive for B. gibsoni infection by microscopic examination of blood smears. Molecular confirmation of these microscopic positive cases for B. gibsoni was carried out by 18S rRNA nested-PCR, followed by sequencing. Nested-PCR for the 18S rRNA gene was also carried out on microscopically B. gibsoni negative samples that detected a higher percentage of dogs (28.6%) infected with B. gibsoni. Genetic diversity in B. gibsoni in India was determined by studying B. gibsoni thrombospondin-related adhesive protein (BgTRAP) gene fragments (855bp) in 19 isolates from four north and northeast states of India. Phylogenetic analysis of the BgTRAP gene revealed that B. gibsoni parasite in India and Bangladesh formed a distinct cluster away from other Asian B. gibsoni isolates available from Japan, Taiwan and Korea. In addition, tandem repeat analysis of the BgTRAP gene clearly showed considerable genetic variation among Indian isolates that was shared by B. gibsoni isolates of Bangladesh. These results suggested that B. gibsoni parasites in a different genetic clade are endemic in dogs in India and Bangladesh. Further studies are required for better understanding of the genetic diversity of B. gibsoni prevalent in India and in its neighbouring countries.

Development of recombinant BgP12 based enzyme linked immunosorbent assays for serodiagnosis of Babesia gibsoni infection in dogs

Indirect ELISA and dot-ELISA using recombinant BgP12 (rBgP12) were developed for the diagnosis of Babesia gibsoni infected dogs. The complete open reading frame of BgP12 gene (378bp) was cloned in pET-32a(+) expression vector and expressed in Escherichia coli as a soluble thioredoxin (Trx) fusion protein. The purified rBgP12 was used for production of anti-rBgP12 rabbit serum, which recognized a native 12-kDa protein in B. gibsoni infected erythrocyte by Western blot analysis. To evaluate the potential of rBgP12 for the serodiagnosis of B. gibsoni, a panel of serum/plasma samples from dogs infected with B. gibsoni (n=13), uninfected sera (n=13) and sera from dogs infected with other haemoparasites viz., Babesia canis vogeli (n=3), Ehrlichia canis (n=3), Hepatozoon canis (n=1) and Dirofilaria immitis (n=1) were used in ELISA formats. In addition, the performance of rBgP12 based indirect ELISA and dot-ELISA were evaluated using 75 serum/plasma samples collected from suspected dogs, in respect to the nested PCR as reference test. The diagnostic sensitivities of indirect ELISA and dot-ELISA were 94.59% and 89.18%, respectively, while their specificities were 84.21% and 81.57%, respectively. Moreover, both the assays using rBgP12 showed no cross reaction with sera from dogs infected with other common haemoparasites indicating their high specificity. High kappa values of indirect ELISA and dot-ELISA indicated the potentials of these assays with substantial agreement at 95% confidence level. It is concluded that indirect ELISA and dot ELISA using rBgP12 might be used in large scale epidemiological surveys and clinical diagnosis of B. gibsoni infection in dogs.

Evaluation of Gastrothylax crumenifer antigenic preparation in serodiagnosis of paramphistomiasis in sheep

An evaluation of Gastrothylax crumenifer crude antigen preparation viz., Somatic Antigen (SAg), Excretory Secretory Antigen (ESAg) and Egg Antigen (EAg) in serodiagnosis of disease was undertaken. Test sera samples were obtained from 30 Paramphistomiasis Positive and 30 Gastrothylax free sheep slaughtered at Hazratbal Kashmir. The referral antigenic preparation were evaluated against Paramphistomiasis positive sera, via., control negative sera, using double immunodiffusion test (DID), (IEP) Immunoelectrophoretic assay and ELISA. The performance of referral antigens, as assessed from percent sensitivity and specificity, revealed an increasing trend from DID (Double immunodiffusion-An immunological technique used in the detection, identification and quantification of antibodies and antigens) to IEP (immunoelectrophoresis-A general name for a number of biochemical methods for separation and characterization of proteins based on electrophoresis and reaction with antibodies), followed by ELISA, detecting higher number of sheep positive for paramphistomiasis. In ELISA the ESAg and SAg were evaluated as most reactive antigens with no significant difference and EAg was the least antigenic. In IEP, EAg had the higher sensitivity (60%) and analogous specificity of SAg and ESAg. The formation of the preceptin lines in the proximity to EAg containing wells (cathode end) in IEP was suggestive of higher molecular weight of G. crumenifer specific protein molecules with slower rate of migration. Purification and characterization of G. crumenifer and identification of specific antigenic molecules, particularly in EAg has been suggested for qualitative improvement of diagnostic value of the antigens in the tests used here in.

Th1 and Th2 cytokine gene expression in primary infection and vaccination against Fasciola gigantica in buffaloes by real-time PCR

Th1 and Th2 cytokine gene expression in buffalo calves during primary infection with Fasciola gigantica as well as in response to immunization with the parasite recombinant fatty acid binding protein (rFABP) and recombinant glutathione S-transferase (rGST) proteins was measured at 14th week of infection by real-time PCR with the double-stranded DNA-binding dye SYBR Green. Experimental animals were randomly distributed into FABP, GST, cocktail, challenge and healthy groups. Animals in groups FABP and GST were immunized with 400 μg rFABP and rGST, respectively, and cocktail group with a mixture of 400 μg each of rFABP and rGST in the neck and thigh muscles. All animals received three immunizations at 3-week interval. Calves were challenged per os with 400 viable metacercariae along with the unimmunized challenge control group 1 month after the last immunization. Expression of various cytokines in response to the immunization and parasite primary infection was measured by real-time PCR. Expression of IL-2 (4.5-fold) and IFN-γ (3.2-fold), followed by IL-6 (1.7-fold) and IL-4 (1.6-fold), with downregulation of TNF-α and IL-10 was observed in response to F. gigantica infection in these animals. However, there was a sharp increase in the expression of the IL-4 (211.93 and 111.81-fold) and IL-6 mRNA (219.22 and 48.29-fold) to GST and FABP immunizations, respectively. A downregulation of the IL-1α, a Th1 cytokine in response to FABP and GST immunization in these calves, was also observed. Overall, a mixed type of Th1 and Th2 cytokine environment was evoked to chronic F. gigantica infection and immunization with the above two recombinant proteins in buffaloes.

Genetic characterization of Fasciola gigantica from different geographical regions of India by ribosomal DNA markers

Ribosomal DNA sequences of the second internal transcribed spacer (ITS-2) and 28S ribosomal DNA (618 bp) of Fasciola gigantica collected from cattle and buffaloes from four different geographical locations of India, were characterized for genotyping. ITS-2 sequence was analyzed in 28 worms that was typical of F. gigantica and differed at six positions, with one of these being a distinguishing deletion (T) at the 327th position in F. gigantica relative to F. hepatica. However, Fasciola specimens also showed intraspecies sequence polymorphism in the ITS-2, with two different ITS-2 sequences existing in the ribosomal DNA (rDNA) array within a single Fasciola worm. One of the sequences was identical to that of F. gigantica and the other showed extensive sequence polymorphism in the ITS-2. Using BspH1-restriction fragment length polymorphism, six variable ITS-2 sequences in F. gigantica were identified within these parasite specimens and were found distributed in these four geographical regions. 28S rDNA sequence of 24 flukes, collected from the above four geographical regions, showed a single nucleotide polymorphism at 284th nucleotide (G/A). Analyzing the sequence data of 28S rDNA of F. gigantica available from some African and Asian countries for this polymorphic 284th nucleotide position, it is proposed that there are two basic lineages of the F. gigantica for 28S rDNA existing in the fluke populations from five African and several Asian countries.

Edible vaccines against veterinary parasitic diseases--current status and future prospects

Protection of domestic animals against parasitic infections remains a major challenge in most of the developing countries, especially in the surge of drug resistant strains. In this circumstance vaccination seems to be the sole practical strategy to combat parasites. Most of the presently available live or killed parasitic vaccines possess many disadvantages. Thus, expression of parasitic antigens has seen a continued interest over the past few decades. However, only a limited success was achieved using bacterial, yeast, insect and mammalian expression systems. This is witnessed by an increasing number of reports on transgenic plant expression of previously reported and new antigens. Oral delivery of plant-made vaccines is particularly attractive due to their exceptional advantages. Moreover, the regulatory burden for veterinary vaccines is less compared to human vaccines. This led to an incredible investment in the field of transgenic plant vaccines for veterinary purpose. Plant based vaccine trials have been conducted to combat various significant parasitic diseases such as fasciolosis, schistosomosis, poultry coccidiosis, porcine cycticercosis and ascariosis. Besides, passive immunization by oral delivery of antibodies expressed in transgenic plants against poultry coccidiosis is an innovative strategy. These trials may pave way to the development of promising edible veterinary vaccines in the near future. As the existing data regarding edible parasitic vaccines are scattered, an attempt has been made to assemble the available literature.

Characterization of excretory-secretory antigens of adult Toxocara canis by western blotting

Toxocara canis is one of the most common helminth worm of dogs which continues to stimulate both public health concern alongside the higher scientific interest. It may cause visceral and ocular damage in humans especially in children. The identification of specific antigens of T. canis is important so as to develop better diagnostic techniques. Excretory-secretory (ES) antigens were prepared by culturing the adult T. canis worms in RPMI 1640 medium without serum supplementation followed by ammonium sulphate precipitation. These antigens were separated using sodium dodecyl sulphate-electrophoresis (SDS-PAGE). Recovered proteins ranged from 30 to 384 kDa. The specific reactivity of the T. canis excretory-secretory (TC-ES) proteins was checked by western blotting. The immuno-reactivity of the naturally infected dog sera with the TC-ES antigens showed five bands at 43, 57,105, 139 and 175 kDa. The immuno-reactivity of the hyper immune serum raised in rabbits against TC-ES antigens was observed with ten polypeptides of 21, 25, 30, 37, 45, 50, 57, 69, 77 and 105 kDa. Common antigens band were observed at 57 and 105 KDa. These antigens merit further evaluation as candidate for use in diagnosis of toxocariasis in humans and adult dogs.

Prevalence of canine toxocariasis in Bareilly, Uttar Pradesh, India

Toxocara canis is one of the most common parasitic helminth worm of dogs and also a causative agent of zoonotic disease in humans. This pilot study was conducted to determine the presence of T. canis infection in dog population in and around Bareilly, Uttar Pradesh, India. A total of 558 faecal samples both from stray and owned dogs were screened and overall 24.3 % dogs were found positive for T. canis. A comparison between owned and stray dogs suggests that the higher prevalence was observed in the latter group. The age of the dogs had a considerable influence on prevalence, with a much higher proportion of younger dogs being infected. Among the stray dogs, the infection rate is much higher (62.79 %) in pups, as compared to 7.8 % in adult. Similarly, of the owned dogs screened 41.74 % pups were infected while the infection rate in adults was only 3.38 %. The higher rate of prevalence of this parasite in dogs could be the source of soil contamination for transmission of Toxocariasis which is of public health importance in this region.

Vaccination of buffaloes with Fasciola gigantica recombinant glutathione S-transferase and fatty acid binding protein

Fasciola gigantica, causative agent of tropical fasciolosis, inflicts substantial economic losses on the livestock industry, affecting severely buffalo productivity in the tropical countries. Very few vaccination trials with different target antigens against F. gigantica infection have been conducted in this host. Present study describes a vaccination trial in buffaloes with F. gigantica recombinant glutathione S-transferase and fatty acid binding protein. The two recombinant proteins were expressed in Escherichia coli and evaluated for their immunoprophylactic potential in buffalo calves, using montanide 70 M-VG, a mineral oil-based adjuvant, for delivering the antigens. Buffalo calves were distributed in three groups, with group I, II and III calves immunized with recombinant glutathione S-transferase, fatty acid binding protein and a cocktail of these two antigens, respectively. Immunization of the calves evoked a mixed IgG1 and IgG2 antibody response. Present vaccination trial in these animals achieved a maximum protection level of 35%, when the two antigens were used in combination. Eosinophils were measured in both immunized and non-immunized challenge control animals, which showed a steady increase in their count in response to immunization with both the antigens and infection with F. gigantica, respectively.

Prevalence of Cryptosporidium andersoni: a molecular epidemiological survey among cattle in India

Cryptosporidiosis is an important and established cause of calfhood morbidity in bovines. The present communication reports the prevalence of Cryptosporidium infection among juvenile and adult cattle (6-24 months old) in India based on examination of faecal samples collected from 350 animals across three different agro-climatic regions of the country and further confirmation by a two-step nested PCR assay targeting 18S ssu rRNA gene. A total of 45 samples were positive for Cryptosoridium species by nested PCR assay. The PCR products were subjected to restriction fragment length polymorphism (RFLP) analysis using SspI and VspI restriction enzymes for species differentiation. The results showed that the species involved in all the samples found positive was Cryptosporidium andersoni. The overall prevalence rate was 12.85%, with highest occurrence in the northern states (14.37%) of the country. The animals between age group of 6-12 months were mostly affected (21.67%) and the season wise prevalence of infection was more during the hot and humid monsoon season (20.16%). The results clearly demonstrated that C. andersoni is the major Cryptosporidium species affecting juvenile and adult cattle in three agro-climatically different geographical regions of India. This is the first report on prevalence of C. andersoni in bovines from India the confirmation of which is based on application of nested PCR and PCR-RFLP based molecular tools.

Prevalence and molecular characterization of bovine Cryptosporidium isolates in India

A survey based on PCR assay of 18S SSU rRNA gene revealed a 30.2% infection with Cryptosporidium spp., out of 457 faecal samples collected from neonatal bovine calves across three different regions of India. The PCR-RFLP pattern of the gene in all the positive cases established the species as Cryptosporidium parvum. Highest prevalence was recorded in the monsoon months (37.3%) and in the calves showing acute diarrhoea (32.3%). The calves below 15 days of age were mostly affected (45.1%). The infection was more prevalent in the northern parts (35.4%) of the country than in the eastern or southern parts. Results indicated that C. parvum was the only species of Cryptosporidium prevalent in bovine calves in three different geographical regions of India.

Interferon-gamma and interleukin-4 expression during Fasciola gigantica primary infection in crossbred bovine calves as determined by real -time PCR

Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) expression in crossbred (Bos taurusxBos indicus) bovine calves during primary infection with Fasciola gigantica was measured. Ten crossbred calves of 1-year age were divided into two groups of five calves each, group I uninfected control and group II calves orally infected with a dose of 1000 metacercariae of F. gigantica. The two cytokines were measured 10, 30 and 75 days post-infection (PI) by real-time polymerase chain reaction (RT-PCR) with the double stranded DNA-binding dye SYBR Green. IL-4 was present in detectable levels in peripheral blood mononuclear cells (PBMCs) of infected animals at 10, 30 and 75 days PI but no IFN-gamma was detected in PBMCs of infected animals at 10 and 30 days PI. However, at 75 days PI, IFN-gamma in two infected animals was present in detectable level. Eosinophil count increased from 2nd fortnight after infection and the increased level persisted till the termination of experiment. Present study indicated that T-cell response during F. gigantica infection was Th2-type during earlier phase of infection, which may be polarized in chronic infection to that of a Th0-type.

Prepatent detection of Fasciola gigantica infection in bovine calves using metacercarial antigen

Metacercarial antigen of Fasciola gigantica was evaluated for early immunodiagnosis of experimental bovine fasciolosis using ELISA and Western blot. In ELISA, the experimental F. gigantica infection was detected as early as 2 weeks post-infection (WPI). The gradual increasing trend of antibody level was observed from 2 to 7 WPI, followed by a plateau, which was maintained up to 14 WPI. In Western blot, sera from experimentally infected calves recognized one distinct polypeptide of 21 kDa in fractionated metacercarial antigen as early as 10th day post infection. From 2 WPI, more polypeptide bands were reacting. Recognition of these protein bands persisted till the end of the experiment (14 WPI). Cattle sera collected from the field showed 34.5% seroprevalence of fasciolosis by ELISA using MAg. Comparative immunoblot studies of metacercarial antigen with anti-Gigantocotyle explanatum and anti-Paramphistomum epiclitum sera revealed that 21 and 25 kDa polypeptides of metacercarial antigen did not cross-react with any of these sera and appear to be unique to F. gigantica and having the desirable qualities of early and specific immunodiagnosis.

Immuno-diagnosis of bubaline fasciolosis with Fasciola gigantica cathepsin-L and recombinant cathepsin L 1-D proteases

Fasciola gigantica cathepsin-L cysteine proteinase and recombinant cathepsin L 1-D were assessed for their potential in the immuno-diagnosis of F. gigantica infection in buffaloes. A diagnostic ELISA, based on these two antigens, was developed to detect antibodies against F. gigantica in water buffaloes. Sensitivity of the ELISA was assessed using sera from buffaloes experimentally or naturally infected with F. gigantica from F. gigantica endemic areas and its specificity by probing the sera of the host from F. gigantica non-endemic area. Our earlier studies under experimental setting showed 100% sensitivity of cathepsin-L ELISA in the diagnosis of fasciolosis in buffaloes, with the earliest detection of infection at 4 weeks post-infection. However, under field situation of natural F. gigantica infection, this sensitivity declined to 97.1% but specificity of the test remained 100%. Cross-reactivity of the antigen was checked with Schistosoma indicum, S. spindale, Paramphistomum epiclitum, Gastrothylax spp., Gigantocotyle explanatum, hydatid and Strongyloides papilossus in the bubaline host, naturally infected with these helminths. F. gigantica cathepsin-L and the recombinant cathepsin L-1D does not cross-react with these helminth parasites in natural mono or mixed infection of the host. The present ELISA contributes a relatively sensitive and reliable tool for the early serodiagnosis of bubaline fasciolosis.

Cathepsin L cysteine proteinase in the diagnosis of bovine Fasciola gigantica infection

Cathepsin L cysteine proteinase from Fasciola gigantica was evaluated for its potential in the early prepatent detection of this helminth infection in bovine calves. Five cross-bred bovine calves were experimentally infected with 400 metacercariae/calf and evaluated for anti-cathepsin L antibody response. F. gigantica infection in these calves could be detected 4 weeks post-infection using an ELISA, dipstick ELISA and Western blotting with 100% sensitivity. The antigen was also used to detect F. gigantica field infection in cattle, by screening 256 sera of these animals by an ELISA, which demonstrated an overall infection rate of 26.95%. Preliminary studies showed that F. gigantica cathepsin L cysteine proteinase does not cross-react with Paramphistomum epiclitum, Gigantocotyle explanatum and hydatid cyst antigens. However, extensive studies on the cross-reactivity of this antigen with related helminth parasites of cattle and buffaloes are required, before this antigen can be considered suitable for immuno-diagnosis of fasciolosis in these ruminants.

Fasciola gigantica cathepsin-L cysteine proteinase in the detection of early experimental fasciolosis in ruminants

Cathepsin-L cysteine proteinase was purified from Fasciola gigantica regurgitant by two-step alcoholic fractionation, followed by ion-exchange chromatography. The purification strategy was evolved to eliminate other contaminating proteins co-precipitating with the purified proteinase during alcoholic fractionation. The enzyme was stable on long-term storage at -20 degrees C rendering it more suitable for field diagnostic use. The purified cathepsin-L cysteine proteinase was assayed for detection of F. gigantica experimental infection in sheep and buffaloes and could detect infection, as early as 4 weeks post-infection by ELISA, Western blotting and Dipstick ELISA. The 28-kDa cathepsin-L cysteine proteinase seems a promising antigen for the diagnosis of tropical fasciolosis in domestic animals.

Vaccination of buffaloes with Fasciola gigantica recombinant fatty acid binding protein

Recombinant fatty acid binding protein (rFABP) of Fasciola gigantica was expressed in Escherichia coli and used as vaccine in Freund's adjuvant to evaluate the level of protection induced in buffalo (Bubalus bubalis) calves. Fifteen buffalo calves were distributed to three groups of five calves each. An antigen dose of 400 mug for each of the three immunizations at 3-week intervals, and a challenge dose of 600 metacercariae was administered per calf. Levels of anti-FABP antibodies increased rapidly by 2 weeks after the first immunization and were always significantly higher in the immunized-challenged group than in the infected control group. Immunization with FABP induced both humoral and cell-mediated immune response in these animals. Vaccination showed a moderate level of protection in terms of reduced fluke burden (35.8%) and liver damage as assayed by aspartate aminotransferase and sulfhydryl group levels as well as anti-fecundity effect of the vaccine.

Humoral immune response against Fasciola gigantica fatty acid binding protein

Recombinant fatty acid binding protein of Fasciola gigantica was expressed in Escherichia coli and purified by nickel chelating affinity chromatography. The recombinant protein along with native fatty acid binding protein (FABP) isolated from the parasite were evaluated for their potential in the diagnosis of F. gigantica infection in sheep, cattle and buffaloes, both by ELISA and western blotting. Results of this study indicate that there is no humoral immune response generated against this protein in the experimental infection of these ruminants with F. gigantica, thereby limiting the usefulness of this antigen in the early diagnosis of fasciolosis in these animals. Also, the paper discusses the probable reasons for the failure of this protein in detecting humoral response in these animals by ELISA and immunoblotting.

Detection of Fasciola gigantica infection in snails by polymerase chain reaction

Polymerase chain reaction (PCR) was used to detect Fasciola gigantica infection in the snail intermediate host. Fasciola specific primers amplified a 124 bp fragment in PCR when the genomic DNA isolated from F. gigantica infected Lymnaea auricularia snails was used as template. In addition to the 124 bp amplicon, a ladder of DNA fragments representing amplification of the 124 bp repetitive sequences was observed. Genomic DNA of the parasite was used as a positive control, which also gave an amplification of the 124 bp fragment. DNA isolated from non-infected snails was used as a negative control and no amplification of this sequence was observed. This technique is highly specific and sensitive and possesses fairly good prospects of its utility as an epidemiological tool for ascertaining the infectivity status in ubiquitous snail populations.

Studies on the prevalence and laboratory transmission of fascioliasis in animals in the Kashmir Valley

In Kashmir, 85.1% of cattle, 51.3% of sheep and 14.8% of goats were found infected with Fasciola spp. The prevalence rate varied from 66.6 to 100.0%, 25.0 to 100% and nil to 66.0% in cattle, sheep and goats respectively in different months of the year. Fasciola gigantica was the predominant species in all animal species but sheep harboured both F. gigantica and F. hepatica. The prevalence of F. hepatica infection in sheep happens to be the first report from India. Lymnaea auricularia sensu stricto supported the development of F. gigantica under laboratory conditions. The incubation temperature affected the shedding of the cercariae. Snails maintained at 25-27 degrees C started cercarial shedding as early as day 20 post-infection (PI), whereas those maintained at 10-12 degrees C commenced it from day 64 PI. One out of three experimentally infected guinea pigs aged 1 month revealed adult flukes in the liver at necropsy on day 52 PI.

Establishment of Ascaridia galli in betamethasone-treated chickens

Twenty-five day-old White Leghorn chickens were each infected orally with 500 (Group I), 1000 (Group II) and 2000 (Group III) infective eggs of Ascaridia galli and were killed 30 days after the infection. A high percentage of the infecting dose (6.5%) established as adult worms in the intestine of chickens receiving the lowest level of primary infection, but as the amount of primary infection given to birds increased, there was a significant fall in the percentage establishment of adult worms in the intestine. A similar pattern of worm establishment was shown by chickens of the same age and receiving similar levels of primary infections, but which were treated with betamethasone at a dose of 2 mg/kg body weight commencing 5 days before and continuing up to 15 days after the infection. Betamethasone-treated birds, however, showed more establishment of worms in the intestine, but lower weight gains in comparison to the birds which were not treated. Different levels of primary infections given, with or without treatment with betamethasone, had no effect on the sex ratio of the resultant male/female worm populations, which became established in almost equal numbers in the intestine of chickens.