Prevalence of flukes (Fasciola hepatica and paramphistomids) in cattle in south-eastern Mexico

The objective of this study was to determine the risk factors and prevalence of trematodes in south-eastern Mexico. The prevalence of trematodes was determined in 1010 bovines. The study was carried out from October 2018 (n=291) to December 2019 (n=719). Only in 2019 rumen and liver fluke eggs were differentiated. Faecal samples (n=311) were obtained from farms in southeast Mexico located in Tabasco, Chiapas and Campeche. In addition, the presence of flukes in liver and rumen from slaughtered cattle in abattoirs was recorded with a total of 408 samples. A logistic procedure was used to obtain the prevalence and the effect of main risk factors such as land physiography (flooded areas and hills), year, sex, animals' age and type of sample obtained (eggs in faeces and flukes). The general prevalence of flukes in cattle was 32.3 % in 2018 and 41.7 % in 2019. Prevalence of F. hepatica (liver fluke) was 18.6 % (134/719) and that of paramphistomids (rumen fluke) was 33.4 % (240/719). The infected cattle from the slaughterhouse indicated a lower prevalence of F. hepatica (1 %) and rumen fluke (26.7 %) than in farms detected by egg in faeces (41.8 % and 42.1 %, respectively). The physiographic zone was decisive in the presence of F. hepatica and rumen fluke, while sex did not represent a risk factor (P > 0.05). The environmental conditions of the Mexican southeast favour the presence of both liver and rumen fluke.

The efficacy of predatory fungi on the control of gastrointestinal parasites in domestic and wild animals-A systematic review

BACKGROUND

Gastrointestinal parasites like nematodes are associated with significant impacts on animal health, causing poor growth rates, diseases and even death. Traditional parasite control includes the use of anthelmintic drugs, albeit being associated with drug resistance and ecotoxicity. In the last decade, biological control of parasites using nematophagous or predatory fungi has been increasingly studied, although systematic evidence of its efficacy is still lacking. The aim of this work was to assess the evidence of efficacy of nematophagous fungi in the control of nematodes and other gastrointestinal parasites in different animal species.

METHODS

Using the PICO method (Population, Intervention, Comparison and Outcomes), we performed a systematic review on the subject to search for original papers published between January 2006 and October 2019, written in English, and indexed in PubMed/Medline. Medical Subject Headings (MeSH) terms were used in the syntax. Papers were selected for detailed review based on title and abstract. Inclusion and exclusion criteria were applied, and relevant data were collected from the remaining papers.

RESULTS

The literature search retrieved 616 papers. Eighty-nine were submitted to a detailed review. In the end, 53 papers were included in the analysis. The studies were very heterogeneous, using different fungi, doses, frequency of administration, duration of treatment, host animals, and target parasites. Considering the 53 papers, 44 studies (83 % of the interventions) showed efficacy, with only 9 studies (17 %) showing no significant differences when compared to control.

CONCLUSION

With the increasing hazards of drug resistance and ecotoxicity, biological control with predatory fungi stands out as a good tool for future parasite management, whether as a complementary treatment or as an alternative to standard parasite control.

Horses are susceptible to natural, but resistant to experimental, infection with the liver fluke, Fasciola hepatica

Fasciola hepatica is a common parasite of livestock in Ireland, causing significant economic losses and affecting animal welfare. A previous abattoir study of 200 horses led to an estimated 9.5 % prevalence of infection in horses slaughtered in Ireland. However, the epidemiology and pathogenic significance of this infection in this species is not well-described. The objectives of this study were to determine the susceptibility of horses to oral challenge infection with F. hepatica metacercariae, and to document the course of the infection along with serological and biochemical response. We attempted an experimental infection of horses (n = 10; 9 geldings and 1 mare) with F. hepatica. Four were given 1000 metacercariae, four 500 metacercariae and two were sham-infected. Blood and faecal samples were taken at intervals up to 18 weeks post-infection (wpi). ELISA assays were used to assess sero-conversion in the experimental horses and also in a panel of sera from horses of known fluke status. No flukes were recovered from any of the livers, and neither were any lesions that could be attributed to F. hepatica infection observed. Coproantigen ELISA was negative throughout for all horses. Three antibody detection ELISAs, useful in diagnosing fasciolosis in other species, had limitations as diagnostic aids as determined using a panel of sera from horses of known F. hepatica infection status. This study is limited by the relatively small number of animals included, and the relatively short duration of the study period. Failure to establish infection after oral challenge raises fundamental questions on the pathophysiology and epidemiology of equine fasciolosis.

Antigen characterization from second instars of oestrid bot flies for the detection of anti-Cephenemyia stimulator antibodies by ELISA in roe deer (Capreolus capreolus)

A study to determine the most appropriate antigen for use in the serodiagnosis of Cephenemyia (Diptera: Oestridae) infestation in roe deer (Capreolus capreolus) was carried out using immunoenzymatic tests. Serum samples from 43 roe deer from northern Spain were obtained post-mortem and corresponding numbers of bot fly larvae established. Three antigen complexes were tested, including Cephenemyia stimulator Clark excretory/secretory antigens (CsES), C. stimulator somatic antigens (CsSA) and Oestrus ovis L. (Diptera: Oestridae) excretory/secretory antigens (OoES). In addition, the composition of each antigen was analysed using an electrophoresis system. Cephenemyia stimulator larvae were found in 25% of roe deer; the mean intensity of infection was 24.3 larvae per infested animal. In the antigen analysis, CsSA showed four exclusive bands of molecular weight (17-19, 62, 65 and 67-70 kDa). A positive correlation between immunoglobulin G (IgG) values and total number of larvae was found with CsES and CsSA. The highest sensitivity value, negative predictive value and negative likelihood ratio were obtained using CsES. The highest specificity value, positive likelihood ratio and kappa value were achieved with CsSA. The predictive values of the enzyme-linked immunosorbent assay (ELISA) using CsES and CsSA reached statistical significance and seroprevalence values were 26-44%. The use of ELISA with CsES and CsSA seems promising in the non-invasive diagnosis of Cephenemyia infestation in roe deer.

Mixed production of filamentous fungal spores for preventing soil-transmitted helminth zoonoses: a preliminary analysis

Helminth zoonoses are parasitic infections shared by humans and animals, being the soil-transmitted helminths (STHs) mainly caused by roundworms (ascarids) and hookworms. This study was aimed to assess the individual and/or mixed production of two helminth-antagonistic fungi, one ovicide (Mucor circinelloides) and other predator (Duddingtonia flagrans). Fungi were grown both in Petri plates and in a submerged culture (composed by water, NaCl, Na2HPO4 · 12 H2O, and wheat (Triticum aestivum)). A Fasciola hepatica recombinant protein (FhrAPS) was incorporated to the cultures to improve fungal production. All the cultured plates showed fungal growth, without difference in the development of the fungi when grown alone or mixed. High counts of Mucor spores were produced in liquid media cultures, and no significant differences were achieved regarding single or mixed cultures, or the incorporation of the FhrAPS. A significantly higher production of Duddingtonia spores after the incorporation of the FhrAPS was observed. When analyzing the parasiticide efficacy of the fungal mixture, viability of T. canis eggs reduced to 51%, and the numbers of third stage cyathostomin larvae reduced to 4%. It is concluded, the capability of a fungal mixture containing an ovicide (Mucor) and a predator species (Duddingtonia) for growing together in a submerged medium containing the FhrAPS offers a very interesting tool for preventing STHs.

Exposure to Sarcocystis spp. in horses from Spain determined by Western blot analysis using Sarcocystis neurona merozoites as heterologous antigen

Horses serve as an intermediate host for several species of Sarcocystis, all of which utilize canids as the definitive host. Sarcocystis spp. infection and formation of latent sarcocysts in horses often appears to be subclinical, but morbidity can occur, especially when the parasite burden is large. A serological survey was conducted to determine the presence of antibodies against Sarcocystis spp. in seemingly healthy horses from the Galicia region of Spain. Western blot analyses using Sarcocystis neurona merozoites as heterologous antigen suggested greater than 80% seroprevalance of Sarcocystis spp. in a sample set of 138 horses. The serum samples were further tested with enzyme-linked immunosorbent assays (ELISAs) based on recombinant S. neurona-specific surface antigens (rSnSAGs). As expected for horses from the Eastern Hemisphere, less than 4% of the serum samples were positive when analyzed with either the rSnSAG2 or the rSnSAG4/3 ELISAs. An additional 246 horses were tested using the rSnSAG2 ELISA, which revealed that less than 3% of the 384 samples were seropositive. Collectively, the results of this serologic study suggested that a large proportion of horses from this region of Spain are exposed to Sarcocystis spp. Furthermore, the anti-Sarcocystis seroreactivity in these European horses could be clearly distinguished from anti-S. neurona antibodies using the rSnSAG2 and rSnSAG4/3 ELISAs.

Application of the analysis of serum antibodies (immunoglobulins M and G) to estimate the seroprevalence of ovine oestrosis and to evaluate the effect of chemotherapy

The analysis of immunoglobulin (Ig) M and IgG serum isotypes as indicators of the presence of Oestrus ovis developmental stages was carried out. A serological survey to discover the seasonal variations in the prevalence of oestrosis in sheep from an oceanic climate area was developed. Six hundred and sixty-nine blood samples were analyzed for the presence of IgM and IgG using an enzyme-linked immunosorbent assay and O. ovis second-stage larvae excretory/secretory antigens. In addition, the effect of an ivermectin-based treatment on the humoral immune response was measured. The percentage of positive animals was 54% for IgM and 55% for IgG. The highest percentages of sheep positive to IgM were recorded in the winter and to IgG in the summer. No animals positive to IgM were detected in the ivermectin-treated sheep. These results seem to underline that oestrosis is a parasitic disease to keep watch for in regions with an oceanic climate. A noninvasive evaluation of the success of chemotherapy seems possible by analyzing the serum IgM response.

A novel second instar Gasterophilus excretory/secretory antigen-based ELISA for the diagnosis of gasterophilosis in grazing horses

We have developed a novel enzyme-linked immunosorbent assay (ELISA) based on excretory/secretory antigens of second instar Gasterophilus for the diagnosis of gasterophilosis in grazing horses. Between January 2007 and January 2009, two experiments were carried out on free-ranging horses in northwest Spain. During the first year, monthly blood samples were collected from a herd of 25 horses. In the second year, a monthly serological survey was conducted for a total of 398 different horses. All the sera were analyzed by ELISA using excretory/secretory antigens from Gasterophilus intestinalis (GphiL2ES) and Gasterophilus nasalis second-stage larvae (GphnL2ES). Climatic data were collected between January 2007 and January 2009 from local meteorological automated stations to establish the weather pattern in the study area. Observations of Gasterophilus eggs on the horses' hair and third instars passed in the faeces were also done. The kinetics of IgG response decreased against GphiL2ES from January to July, increased slowly from August and rose up to January. After a slight decrease in January, the absorbances against GphnL2ES reduced from April to August, when the lowest values were observed. The IgG values rose until the end of the study in January. Third instars were observed in the faeces in March to May, and Gasterophilus eggs were seen on the horses' hair from June to September. The highest IgG seroprevalences were achieved in winter (January-February; 100%) against both antigens. The lowest percentages of seropositivity were observed in June (3%) to the GphiL2ES, and in July (9%) to the GphnL2ES. The use of antigens from G. intestinalis second-stage larvae was shown to be suitable for diagnosing infestation by G. intestinalis or G. nasalis. We concluded that under oceanic climate conditions, the egg-laying period occurs from late spring, and eggs and first instars are found in the mouth in early summer. During summer the second instars move into the stomach and intestine, where the third-stage larvae remain until the end of winter, when pupation takes place. The adult horse bot fly emerges in the spring. Two treatments for the control of gasterophilosis are suggested: a curative in the summer to eliminate the first instars and a preventive in the autumn to suppress the second instars.

Assessment of climatic and orographic conditions on the infection by Calicophoron daubneyi and Dicrocoelium dendriticum in grazing beef cattle (NW Spain)

From February 2003 to March 2004, 1148 faecal samples from autochthonous Rubia Gallega cattle breed were collected in 170 farms from Lugo (NW Spain), in order to find out the prevalence and intensity of egg-excretion by Calicophoron daubneyi and Dicrocoelium dendriticum, and the possible influence of external factors as annual mean temperature and rainfall, altitude and mean slope. Twenty-six percent (95% CI 19%, 33%) and the 18% (12, 24) of the farms were infected with rumen and lancet flukes. C. daubneyi egg-output (Me=24) was found in 13% (11, 15) of the individual samples. Six percent (5, 7) of the animals in the study had low D. dendriticum eggs (Me=8). By estimating the odds ratio values it was shown that the highest probability of infection by C. daubneyi was in pastures with a mean slope of less than 13% (OR=1.9) and situated under 600 m (OR=1.6). Annual mean rainfall and temperature were not identified as risk factors for the infection with rumen flukes. Mountainous pastures with a mean slope of higher than 25% (OR=5.8) and situated over 600 m (OR=24.6) where precipitation was high (>1000 mm; OR=7) and temperature low (<11 degrees C; 2.8) had involved the highest risk of infection by D. dendriticum. Because of the prevalences found in this study, employment of suitable management practices with strategic treatments with efficacious anthelmintics are needed to reduce the presence of both trematodes and to increase the health status of grazing beef cattle.

Immunodiagnosis of current fasciolosis in sheep naturally exposed to Fasciola hepatica by using a 2.9kDa recombinant protein

A 2.9 kDa recombinant-Fasciola hepatica protein (FhrAPS) was employed to estimate the prevalence of fasciolosis in sheep maintained under field conditions. For this purpose, 340 samples with known status in relation to fasciolosis by using a direct-ELISA and the coprological sedimentation were used. These samples were analysed by using an indirect-ELISA (iELISA) and the FhrAPS recombinant protein and excretory/secretory antigens (FhES) of this trematode. Current fasciolosis (CF) was named when results were positive to antigenemia and/or coprology. Out of 198 sheep with current fasciolosis, 68% were positive to the FhrAPS-ELISA test and 53% to the FhES. We observed 14% of the CF-neg sheep were positive to the FhrAPS, whereas this percentage was 52% with the FhES. A significant correlation between FhrAPS and current fasciolosis was obtained (r2=0.513, p=0.001). We concluded that the FhrAPS provides a more suitable antigen than FhES for developing field trials to know the prevalence of early and current fasciolosis.

Analysis of the IgG antibody response against Paramphistomidae trematoda in naturally infected cattle. Application to serological surveys

The IgG antibody response to Calicophoron daubneyi (Digenea: Paramphistomidae) excretory/secretory antigens was evaluated in naturally infected cattle from Lugo (Galicia, NW Spain) by using an ELISA procedure. Two studies were conducted, first a survey in 524 cattle separated into three groups according to age, G-1 (0-2 years old), G-2 (3-5 years old) and G-3 (> 6 years old). In the second study, three groups of cattle were employed: G-I, naturally infected; G-T, naturally infected and treated with oxyclozanide plus levamisole (Nilzan Plus); G-C, cattle maintained in a farm where C. daubneyi has never diagnosed. Variations on egg-output and haematic parameters (erythrocytes, haematocrite, leukocytes and lymphocytes) were also analyzed. The ELISA procedure showed that 61.2% of the cattle in the first study had been exposed to the trematode, but only 10.1% passed eggs in the feces. Age-association with egg-output was shown but not with the IgG values. In the second experiment, the administration of the anthelmintic reduced significantly the IgG kinetic levels and the C. daubneyi-egg-output was suppressed during 12 weeks in the G-T group. The values of red cells, haematocrite, leukocytes and lymphocytes increased significantly in the treated cattle 5 weeks after chemotherapy; however, new reduction after week 5 was recorded, as results of the challenge of these cattle. This is the first investigation in which evaluation of the IgG humoral response against C. daubneyi in cattle has been carried out. We proved that a notable IgG response in naturally infected cattle is induced, and can be detected by using an ELISA procedure. The IgG antibodies did not increase after challenge infection. Our results proved an important percentage of cattle were exposed to this trematode in the area of study and suitable measures for preventing this relationship must be considered.

Toxocara canis larvae viability after disinfectant-exposition

The effect of three routinely used disinfectants on the embryonary development of Toxocara canis eggs was evaluated both in vivo and in vitro. In the in vitro experiment, T. canis eggs were treated with the ethanol, sodium hypochlorite, and one commercial mix of benzalconium chloride and formaldehyde, and the embryonary development was assessed. After a period of 24 days incubation, ethanol was the best disinfectant because it prevented the development of the T. canis larvae 2 in the eggs, and sodium hypochlorite caused degeneration in 50% eggs. By using the commercial mix, 25% T. canis eggs developed to 2nd stage larvae. In the in vivo experiment, the embryonated eggs treated with the disinfectants were inoculated to mice, and their brain tissues were examined for larval presence on the 24th day postinfection. In addition, a control group was set up for comparison with the infected groups. No injury or T. canis larvae were observed in mice infected with sodium hypochlorite-treated eggs, opposite to that recorded in the animals infected with the commercial disinfectant-treated eggs. These results showed that both ethanol and sodium hypochlorite are very appropriate because of their full efficacy against infective T. canis eggs. Disinfection of kennels, animal shelters, cages, and veterinary clinics with one of these products to eliminate T. canis eggs and to avoid contamination is strongly recommended.

Prevalences of gastrointestinal parasites in sheep and parasite-control practices in NW Spain

A coprological survey to know the presence of gastro-intestinal nematode parasites infecting sheep was done in Galicia (NW Spain), an area with Atlantic climate where sheep production is replacing cattle due to the Agricultural Community Politics of the European Union. From September 2001 to November 2002, 1710 faecal samples were randomly collected from 49 sheep farms and examined by using the flotation technique to determine the prevalence of gastro-intestinal nematode parasites. The sheep-level prevalence was 100%, and the genera identified were Chabertia, Cooperia, Haemonchus, Nematodirus, Oesophagostomum, Teladorsagia, Trichostrongylus and Trichuris spp. A questionnaire was distributed to the farmers (at the same time as sampling) about parasite-control practices during the year before sampling (2000). Ninety percent (95% CI 81%, 98%) of the farmers said they used antiparasitic drugs occasionally, but none of them asked for a coprological analysis prior to the treatment and the efficacy of the drugs was never evaluated. A higher median EPG was observed in the treated sheep (163) than in the untreated ones (26). Chemotherapy was the only parasite-control practice. Flocks that treated according to the farmer's previous experience had higher median EPG (236) than other flocks (185 following the prescription of their veterinary clinician and 232 based on the commercial agent's counsel). Typically, one benzimidazole-treatment per year was applied in autumn and non-veterinary counsel was used. Sheep treated with imidotiazoles had lower EPG (144) than other drugs (164 for the benzimidazoles and 166 for the macrocyclic lactones). We found a higher median EPG in the sheep receiving two treatments/year (175) than in those treated only once per year (156). These results suggest lack of knowledge about worm-control strategies and anthelmintic use or unwillingness to apply such knowledge.

A 2.9 kDa Fasciola hepatica-recombinant protein based ELISA test for the detection of current-ovine fasciolosis trickle infected

The suitability of an enzyme linked immunosorbent assay (ELISA) test with a 2.9 kDa Fasciola hepatica-recombinant protein (FhrAPS) for diagnosing early and current-ovine fasciolosis was analyzed, and compared to that obtained by using a direct ELISA for detecting F. hepatica-circulating FhES antigens and to the coprological sedimentation for fluke egg quantitation. Fourteen Gallega autochthonous breed sheep were experimentally infected with metacercariae by a trickle system (small repetitive infections) and divided into two groups: G-I represented a primary infection for 34 weeks; G-R, animals with primary infection and reinfected 18 w.a.p.i. Seven sheep were left uninfected as the control group (G-C). Serum IgG antibody values against the FhrAPS rose rapidly by 1st w.a.p.i. in all infected sheep. Antibody levels in those with primary infection (G-I, G-C) peaked at 10 weeks, diminishing slightly and levelling from 16 to 34 weeks. Those with primary infection reinfected at 18 weeks had a rebound effect with the highest values observed. Circulating F. hepatica-ES antigens were detected by the 1st w.a.p.i. in all infected groups peaking at 6 weeks, decreasing rapidly to uninfected control values by 10 weeks of infection. Faecal egg-output started 11 weeks after primary infection. An increase in the IgG antibody as well as antigen responses to the FhrAPS and to anti-FhES from the 18 w.a.p.i. was recorded in G-T and G-R after the challenge infection. Antibody levels remained high whereas antigenemia values diminished after 6 weeks. A positive significant correlation between the IgG response against the FhrAPS and the F. hepatica circulating antigens (r2 = 0.428, p = 0.001) was obtained. In conclusion, our standardized diagnostic ELISA for fasciolosis based on the detection of IgG responses to the FhrAPS would be a valuable tool to diagnosis early and current F. hepatica-infections in sheep.

Analysis of the humoral immune response to Oestrus ovis in ovine

Antibody responses (IgG, IgM and IgA) against Oestrus ovis were analyzed in sheep and in first year grazing lambs from Sardinia (Italy) by an indirect-enzyme-linked immunoassay test and L2 O. ovis excretory/secretory antigens. Serum samples from 208 sheep were obtained prior to be slaughtered, and then heads were removed and cut open along their longitudinal axis to collect the parasites from the nasal cavities, turbinates and sinus. Besides this, blood samples were monthly collected from the lambs of G-1 (maintained under field conditions) and the lambs of G-2 (kept housed since birth to avoid Oestrus infestations) throughout a year. In the sheep, a positive significant correlation was observed between the number of first instar O. ovis larvae and the values of IgM, and between the second instar larvae and the IgG optical densities. In the lambs, all classes of antibodies increased significantly from July in G-1. The highest values of IgG were reached in September (IgG) and decreased in November-December. The IgM response peaked in November, and very low values of IgA were observed during the study. Matching these data with chronobiology of O. ovis in this region, we conclude that the first infection occurs on May, stimulating the production of humoral antibodies. The reduction of the IgG antibody levels starting from October means the beginning of the diapause while the IgM response seems to be associated to the presence of L1 in the nasal cavities. The data obtained led us to forecast an early treatment of the ovine on June-July, which should keep away from the maturation of O. ovis L1 larvae, avoiding the development of clinical lesions and interrupting the life cycle of this parasite.

Comparison of Oestrus ovis metabolic and somatic antigens for the immunodiagnosis of the zoonotic myasis oestrosis by immunoenzymatic probes

Control of zoonosis implies reduction of infected animal hosts, and the first measure consists of a suitable and accurate detection test. An experimental study for determining the most appropriate antigen (metabolic or somatic) to be used in the detection of the oestrosis (Oestrus ovis) zoonotic myasis by means of immunoenzymatic probes was carried out. A flock of 23 uninfected goats was maintained under field conditions to allow their infection in Sassari (Sardinia, Italy). Caprine were bled monthly and serum samples processed by means of an iELISA. After comparing these results to the chronobiology of O. ovis, we proved that the IgG humoral response against the metabolic antigens increased only during the period of real risk of infestation (when adults fly, from May to September), whereas the absorbances against the somatic products were positive from the beginning of the study (in January, prior to infection). We concluded that the excretory/secretory products are most useful and suitable for the immunodiagnosis of oestrosis in goats, because a direct relation between the development of O. ovis and the IgG humoral response is possible, allowing a more accurate diagnostic.

Isolation, identification and expression of a Fasciola hepatica cDNA encoding a 2.9-kDa recombinant protein for the diagnosis of ovine fasciolosis

A 400-bp Fasciola hepatica cDNA clone was isolated from an expression library by immunological screening using rat sera taken 2 weeks after experimental infection. The nucleotide sequence of the cDNA revealed the presence of an open reading frame of 78 bp which encoded a 25 amino acid polypeptide with a predicted molecular weight of 2.9 kDa. This polypeptide was expressed in bacteria as a GST-fusion protein and used for the production of specific antigen. The 2.9 kDa recombinant protein (APS) was evaluated against sera from experimentally infected sheep using an indirect ELISA, and the results were compared to those obtained using F. hepatica excretory/secretory products (ESP). The pattern of IgG was very similar both against the recombinant and the native proteins, increasing early following the infection. After treatment with triclabendazole, the IgG response against the APS seroreverted to negative values, whereas it remained elevated against the ESP. We conclude that this recombinant protein could be used in diagnostic assays for the identification of recently infected sheep.

Prevalence of natural ovine fasciolosis shown by demonstrating the presence of serum circulating antigens

The prevalence of fasciolosis in sheep (Galicia, Northwest Spain) kept under field conditions was determined by using a sandwich-enzyme-linked immunosorbent assay (sELISA). Serum Fasciola hepatica circulating antigens were captured by means of a rabbit polyclonal IgG antibody to F. hepatica excretory/secretory products. Results were compared to those obtained by faecal sedimentation and an indirect ELISA (iELISA) and excretory/secretory antigens. Prevalences were 39.1% by sELISA, 30.4% by faecal sedimentation and 56% by iELISA; 83.3% of the sheep were positive to any one of the three tests. We observed that 59.5% of the sheep examined had active fasciolosis, 29.1% (117) had antigenaemia, 20.4% (82) passed eggs, and 40 (10%) were positive to both probes. We conclude that there is a high prevalence of fasciolosis in sheep from the studied region, and that the combination of sELISA and coprological sedimentation is extremely helpful for demonstrating current fasciolosis, so its application can be strongly recommended for epidemiological surveys.

Diagnosis of parasitic zoonoses by immunoenzymatic assays--analysis of cross-reactivity among the excretory/secretory antigens of Fasciola hepatica, Toxocara canis, and Ascaris suum

Several parasitic infections such fasciolosis, toxocariosis or ascariosis are important zoonoses. During the infection with Fasciola hepatica, Toxocara canis and Ascaris suum, an important intraorganic phase in their hosts takes place, releasing antigens responsible for a humoral immune response, which enables the diagnosis of that parasitosis. A study to identify the existence of cross-reactivity among the excretory/ secretory antigens of F. hepatica, T. canis and A. suum was developed. One group of Sprague-Dawley rats was infected with 20 metacercariae of F. hepatica and another group remained uninfected as control. By means of an Indirect-ELISA, the rat humoral immune response (IgG and IgM) against the excretory/secretory antigens of F. hepatica was analysed and measured for cross reactivity with T. canis and A. suum. IgM cross-reaction was mainly observed in the first 10 weeks post-infection. IgG cross-reaction was observed throughout the study, and was maximal at the 2-3 weeks and 3-6 weeks post-infection, which corresponds to the intraorganic migratory phase of these parasites. The western-blot showed that the rat IgG recognised three proteins of 190, 160 and 33 kDa in the antigens from F. hepatica, T. canis and A. suum. The existence of cross-reactivity among these antigens seems to demonstrate also the presence of structural similarities, such as tegumental proteins. These results should be consider when immunoassay probes are used in the diagnosis of parasitic infections.

Effect of treatment on the dynamics of circulating hypodermin C in cattle naturally infested with Hypoderma lineatum (Diptera: Oestridae)

An antigen capture ELISA, using a murine monoclonal antibody recognising recombinant hypodermin C (rHyC), was used to evaluate the influence of early treatment with eprinomectin (Eprinex) or fenthion (Spotton) on the kinetics of circulating hypodermin C in calves naturally infested with Hypoderma lineatum. No viable larvae were collected from treated animals, whereas a variable number of warbles were found in control animals. Treatment provoked a decrease in circulating HyC levels that was significant 9 days post-treatment (p.t.). Circulating antigen levels in the treated cattle remained detectable for approximately 99 days p.t. In contrast, control animals had no detectable antigen at 64 days p.t., 42 days earlier than in the treated animals. These results suggest that larvae were either gradually killed, resulting in slow release of antigen or they were encapsulated, leading to the slow liberation of antigen. Kinetics of circulating HyC did not differ among the two insecticide treatments. Antibodies persisted, in all groups, throughout the 120-day study. These results suggest that the antigen capture ELISA will be useful as a technique for detecting successful treatment of cattle grub infestations and for the detection of new infestations in previously infested cattle.

Serum antibodies to Dicrocoelium dendriticum in sheep from Sardinia (Italy)

An indirect enzyme-linked immunosorbent assay (ELISA) with Dicrocoelium dendriticum excretory/secretory antigens was used to evaluate the presence of serum antibodies against the trematode in 738 sheep randomly chosen in Sardinia (Italy). Coprological sedimentation was used to discover egg-output. Seropositivity was detected in 86.2% tested sheep, whereas faecal prevalence was 6.7%; all that were faecal-positive also were ELISA-positive.

Chronobiology of Oestrus ovis (Diptera: Oestridae) in Sardinia, Italy: guidelines to chemoprophylaxis

Oestrus ovis (Linné 1761) larvae are obligatory parasites of the nasal and sinus cavities of sheep and goats. Infestation is prevalent in hot and dry regions, such as Mediterranean countries. The current work was developed to establish the chronobiology of O. ovis in Sardinia, to determine the most suitable time for chemoprophylaxis. A survey was carried out during 1998, and sheep heads were collected monthly from local flocks. A total of 443 heads was examined, and the prevalence of oestrosis was 73.8%. We collected 2,691 larvae (mean = 6.07 +/- 9.52), and the intensity was greatest in November. The humoral immune response against the nasal bot fly was analyzed by means of an indirect-ELISA using second-instar O. ovis excretory and secretory antigens. A seasonal variation in the antibody levels was observed, increasing from April and peaked in June and in September. A significant correlation was observed between first instar intensity and the mean relative humidity (r2 = 0.120; P < 0.05), and between second-instar intensity and the mean temperature (r2 = 0.241; P < 0.05). Three periods in the chronobiology of O. ovis were defined: diapause (October-February), the active phase ofthe endogenous cycle (March-September) and the exit phase (May-September). Our results showed that treatment in October-November was suitable, because first instars were in diapause, preventing the development of first into second instars, and second into third instars.

Influence of age and breed on natural bovine fasciolosis in an endemic area (Galicia, NW Spain)

An analysis was undertaken of the effect of breed and age on bovine fasciolosis using antibody and antigen detection ELISAs. A total of 84.3% of the 1284 serum samples examined had positive antibody values and 20.4% exhibited antigenaemia. The seroprevalence of antibodies in crossbred cattle was higher than that in autochthonous Rubia Gallega, Friesian or Brown Swiss cows. The highest percentage antigenaemia occurred in the Brown Swiss cattle, but the breed differences were not statistically significant. Cattle aged 3-5 years had the highest antibody and circulating antigen prevalence and the age differences were significant. It was concluded that the apparent influence of breed was probably closely associated with the husbandry system. The autochthonous Rubia Gallega may be better adapted to fasciolosis as its percentage of antigenaemia was the lowest.

Time-course analysis of coproantigens in rats infected and challenged with Fasciola hepatica

The influence of a challenge infection during an acute or chronic primary infection on Fasciola hepatica-coproantigen kinetics was established in rats. Egg-output and IgG humoral responses were also established. Two primary-infected groups were reinfected at different periods, one 4 weeks after primary infection (w.p.i.) (acute phase) and the other 11 w.p.i. (chronic phase). Another group remained without reinfection as a control. Coproantigens were first detected in the group challenged on acute fascioliasis. The highest values of coproantigens were recorded in the group reinfected during acute fascioliasis and the lowest in the group challenged during chronic fascioliasis. The IgG responses to F. hepatica excretory/secretory antigens increased after reinfection. Neither the egg output nor the parasitic burden were significantly different among the three infected groups. Our results indicate that the time of challenge affects the kinetics of coproantigens. Thus, challenge during acute fascioliasis favours the migration of the juvenile flukes from the primary infection to the bile ducts, and is responsible for the earlier presence of coproantigens in these animals. The possible relationship between coproantigen detection and T1 and T2 tegumentary antigens is discussed.

Effect of fasciolicides on the antigenaemia in sheep naturally infected with Fasciola hepatica

A study was developed to evaluate the influence of triclabendazole (Fasinex) and netobimin (Hapasil) the antigenaemia in sheep naturally infected with Fasciola hepatica during 16 weeks. A sandwich-ELISA (enzyme-linked immunosorbent assay) using a rabbit polyclonal IgG antibody to F. hepatica antigens was employed and the data obtained were compared to those from coprological and indirect-ELISA techniques. Triclabendazole reduced the values of circulating antigens at weeks 2-4 post-treatment and faecal output at weeks 2-8 post-treatment, but antibodies showed positive values until the end of the study. Netobimin did not reduce circulating antigens of the trematode nor egg-excretion; and IgG antibodies did not decrease throughout the study.

Use of a sandwich-enzyme-linked immunosorbent assay (SEA) for the diagnosis of natural Fasciola hepatica infection in cattle from Galicia (NW Spain)

An indirect-enzyme immune-linked immunosorbent assay (IEA) was compared to a sandwich-enzyme-linked immunosorbent assay (SEA) to diagnose fasciolosis in naturally infected cattle. By means of a rabbit polyclonal IgG antibody to F. hepatica antigens, captured circulating antigens were detected by an SEA technique. A total of 85.1% of the samples examined was considered positive by using the IEA-test, whereas this percentage was of 37.3% by the SEA test. Using the two enzymatic probes, only the 38.3% resulted positive to both immunoassay probes. Our data indicate that circulating antigen detection assay in combination with results of antibody detection may offer a more reliable diagnostic technique than classic coprologic ones, with results very appropriate for epidemiologic studies carried out on a wide area.