Clinical survey of antibodies against red blood cells in horses after homologous blood transfusion

Serum samples of 20 horses were evaluated for antibodies against RBC after homologous blood transfusion. Transfusion-associated antibodies against RBC were detected in 10 horses. Antibodies recognizing horse blood group antigens Aa, Ae, Db, and Dc were identified. Antibodies against Aa were found in all samples from Aa-negative horses that were transfused with Aa-positive RBC. Antibodies against Aa persisted for at least 1 year after transfusion. Antibodies against Ae were detected in 7 of 8 horses transfused with Ae-positive RBC. Initial appearance and persistence of antibodies against Ae differed among the horses; antibodies were initially detected 1 week to 154 weeks after transfusion and disappeared as early as 4 weeks after transfusion. Antibodies against Db or Dc were detected in less than or equal to 33% of the horses that lacked Db or Dc antigens and were transfused with Db- or Dc-positive RBC. Antibodies against Db and Dc were initially detected in sera later than were the A-system antibodies. Three mares with transfusion-associated antibodies subsequently produced healthy offspring. Two foals had RBC antigens corresponding to their dam's alloantibodies; maternal colostrum with antibodies against Aa was withheld from the Aa-positive foal. The Db-positive foal remained healthy after nursing the mare with serum antibodies against Db.     

Comparison of an indirect haemagglutination assay and an ELISA for diagnosing Fasciola hepatica in experimentally and naturally infected sheep.

An enzyme-linked immunosorbent assay (ELISA) with somatic (S) or excretory-secretory antigens (ES) was compared with an indirect haemagglutination assay (IHA) for ability to detect antibodies against Fasciola hepatica in sheep. The specificity of both assays was determined by testing sera collected from sheep experimentally or naturally mono-infected with Fasciola hepatica, Haemonchus contortus, Ostertagia circumcincta, Cooperia curticei, Taenia ovis, Eimeria spp., Trichostrongylus vitrinus, Trichostrongylus colubriformis or Nematodirus battus respectively. With S or ES antigens the specificity of the ELISA was 98% or 95% respectively, whereas the specificity of the IHA was 86%. Antibodies directed against Fasciola hepatica were detected by the ELISA with S or ES antigens from 2 weeks after infection until the end of the experiment, whereas the IHA detected antibodies from week 3. We conclude that the ELISA with S antigens compares favourably with the IHA and can be used for the serodiagnosis of ovine fasciolosis in the Netherlands.     

Local antibody responses in the bile and faeces of sheep infected with Fasciola hepatica

The effect of infection with the liver fluke Fasciola hepatica on serum, bile and faecal immunoglobulin and antibody levels was studied in Scottish Blackface sheep. In the serum the immunoglobulins showing the most marked increase were IgG1 and IgG2 and their maximal values were reached at 16 weeks after infection. In the bile IgG2 rose to peak values at two weeks and IgG1, IgA and IgM were maximal at four weeks after infection. The levels of faecal IgG and IgA were low after primary infection but after reinfection a rapid increase in IgA concentration was observed within one to two weeks. Haemagglutinating antibody levels against egg antigens, juvenile and adult excretory-secretory antigens and adult fluke somatic antigens were evaluated. In the sera high titres were observed starting from two to four weeks after infection and persisting until 14 to 16 weeks. Bile haemagglutinating antibodies against excretory-secretory antigens showed the highest level at two and four weeks after infection while antibodies against adult somatic antigens reached maximal titres between four and eight weeks. Faecal antibody levels after primary infection were low but increased rapidly within two weeks after reinfection, coinciding with the elevation in faecal IgA concentration. However, there was no reduction in the number of flukes established in reinfected animals.     

Alloimmunity does not protect from challenge with the feline immunodeficiency virus

Immune responses against polymorphic host molecules incorporated into lentiviral envelopes during cell budding have induced protection against primate immunodeficiency virus infection. Dendritic cells (DCs) express high levels of MHC molecules and are infectable by lentiviruses. Therefore, in this pilot study we addressed the hypothesis that immunization of cats with allogeneic DC would induce immune responses that protect against challenge with the feline immunodeficiency virus. Two groups of 3 cats each received 3 subcutaneous injections of allogeneic or autologous DC, and were then challenged with viruses propagated in the immunizing DC. Infection status and lymphocyte parameters of cats were assessed during 6 weeks after challenge. MHC II antigens were incorporated into viral particles as identified by Western blot; and antibodies reactive with MHC class II antigens were detected in the serum of cats immunized with allogeneic but not autologous DC. After challenge, all cats had proviral DNA in blood leukocytes from 2 weeks post-challenge onward and seroconverted. Cats immunized with allogeneic DC maintained higher total and CD21(+) lymphocyte concentrations, and higher CD4(+)/CD8(+) lymphocyte ratios; however, these differences were not significantly different from cats that received autologous DC immunizations. Plasma viral load was not significantly different between groups of cats (p=0.204). These results suggest that immunization of cats with allogeneic DC does not induce protective immunity against FIV infection.     

Marek's disease in Japanese quails (Coturnix coturnix japonica): a study of natural cases

Marek's disease was observed in quails. Gross lesions were confined mostly to the spleen and liver. Microscopic lesions were commonly seen in spleen, proventriculus, liver, and duodenum. Skin, peripheral nerves, and other visceral organs were also involved. Of 123 quails examined, 39 had serum antibodies against Marek's disease. These antibodies were detected from 11 to 17 weeks of age; the highest incidence was recorded at 15 weeks. Feather follicular antigen detected in 30 of the 95 quails was comparable to that of chicken. The disease was experimentally reproduced in susceptible quails. Marek's-disease-tumor-associated surface antigens (MATSA) were demonstrated in the peripheral leukocytes and spleen cells of affected quails. The possible source of infection and its epidemiological importance are discussed.     

Preparation of Mycoplasma hyopneumoniae antigen for the enzyme-linked immunosorbent assay.

Methods of preparation of Mycoplasma hyopneumoniae antigens for the enzyme-linked immunosorbent assay to detect specific antibody, and properties of the antigens, are described. The reactivity and specificity of antigen prepared by Sephacryl S-300 column chromatography after treatment of M. hyopneumoniae cells with Tween 20 (S-300 antigen) were superior to those of antigen prepared by Sephadex G-25 column chromatography after treatment with Tween 20, or to lipid antigen. There were no differences among strains MI-3, J and VPP11 of M. hyopneumoniae. The S-300 antigen did not show cross-reactivity against porcine hyperimmune sera produced by M. hyorhinis, M. hyosynoviae, M. hyopharyngis, M. flocculare and Acholeplasma granularum. Antibody was first detected in sera of pigs inoculated intranasally with M. hyopneumoniae at two to four weeks after inoculation and seven to eight weeks after pigs were contact-exposed to the same mycoplasma.     

Immunological parameters in goats experimentally infected with SRLV genotype E, strain Roccaverano

Genotype E of small ruminant lentivirus has been recently described in goats from different breeds in Italy. Genotype E infection may differ from known genotypes since deletions of dUTPase and VPR proteins have been confirmed in different independent areas and goat breed, and play a key role on virus replication and pathogenesis. In particular, genotype E Roccaverano strain has been described as low pathogenic since does not lead to clinical symptoms in goats. In contrast, classical CAEV infected goats of the same area and breed presented arthritis. In this study, we have used intratracheal and intra-bone marrow routes to establish genotype E persistent infections. Humoral and cellular immune responses elicited in the host against genotype E and genotype B derived antigens were evaluated until 200 days post-inoculation. Compared to genotype B antigen, seroconversion against genotype E GAG P16-25 antigen was detected at 2-3 weeks after inoculation, significantly earlier and at higher titres. Interestingly, antibody avidity did not increase in the course of the experiment neither against P16-25 nor against SU5, both derived from genotype E. T cell proliferation against P25-GST fusion protein antigens derived from genotype E was firstly detected at 15 days post-inoculation and was maintained throughout time until week 20 post-infection, while T cell proliferation against the genotype B P25 was not produced by the end of the experiment at 20 weeks post-inoculation. The strength of reaction was also higher when using P25 E as stimulator antigen. In contrast with antibody and T cell proliferation, cytotoxic-T-lymphocyte (CTL) activity in the circulating lymphocytes (effector cells) using blood-derived macrophages (BDM) as target cells, was not strain specific being surprisingly higher against genotype B infected antigen presenting cells (APCs). This is the first study reporting experimentally induced immunological changes in SRLV genotype E infection and indicates that CTL activity may be the adaptive immune response able to induce protection against heterologous infection.     

Characterization of the humoral immune response in alpacas (Lama pacos) experimentally infected with Fasciola hepatica against cysteine proteinases Fas1 and Fas2 and histopathological findings

A characterization of the humoral immune response of alpacas to Fasciola hepatica Fas1 and Fas2 antigens, two abundant cysteine proteinases in the excretory/secretory (E/S) products, was performed over the course of 6 months of experimental infection. Six adult alpacas aged 1-2 years old received a single dose of 200 F. hepatica metacercariae; two non-infected alpacas were kept as control group. All infected animals shed eggs 8 weeks post-infection (PI) and the number of flukes recovered at necropsy averaged 41+/-4. The livers of infected animals showed regions with chronic inflammation, granuloma containing parasite eggs, necrosis and cirrhosis. Peripheral eosinophilia in infected animals was greatly enhanced 6 weeks post-infection and later. A single peak of serum glutamic piruvic transaminase (SGPT) was observed 4 weeks PI and serum glutamic oxalacetic transaminase (SGOT) elevated 3 weeks PI and later. Circulating IgG Abs against Fas1 and Fas2 were measured by enzyme-linked immunosorbent assay (ELISA). Fas2-ELISA detected the infection 10 days PI reaching to highest titer on 7-8 weeks PI and kept elevated, until the end of infection. Fas1-ELISA detected the infection 2 weeks PI and followed the same pattern as Fas2-ELISA. Anti Fas2 IgG Abs were in higher titers and showed stronger avidity than anti Fas1 IgG Abs. In addition, rabbit IgG antibodies raised against cysteine proteinase Fas2 showed infiltration of this parasite antigen associated to the degradation of bile ducts and liver parenchyma of infected alpacas. In the present study we have established a F. hepatica experimental infection of alpacas, Fas2 appears to have a role in the pathogenesis of the liver damage in alpacas caused by the liver fluke. Infected alpacas elicited a strong humoral immune response against fluke cysteine proteinases Fas1 and Fas2, which might be considered as candidates for immunodiagnosis and vaccine development against fasciolosis in alpacas.     

Effect of immunization route on mucosal and systemic immune response in Atlantic salmon (Salmo salar)

This study aimed to assess systemic and mucosal immune responses of Atlantic salmon (Salmo salar) exposed to two protein-hapten antigens – dinitrophenol (DNP) and fluorescein isothiocyanate (FITC) each conjugated with keyhole limpet haemocyanin (KLH) – administered using different delivery strategies. Fish were exposed to the antigens through different routes, and were given a booster 4 weeks post initial exposure. Both systemic and mucosal antibody responses were measured for a period of 12 weeks using an enzyme-linked immunosorbent assay (ELISA). Only fish exposed to both antigens via intraperitoneal (IP) injection showed increased systemic antibody response starting 6 weeks post immunization. No treatment was able to produce a mucosal antibody response; however there was an increase in antibody levels in the tissue supernatant from skin explants obtained 12 weeks post immunization from fish injected with FITC. Western blots probed with serum and culture supernatant from skin explants showed a specific response against the antigens. In conclusion, IP injection of hapten-antigen in Atlantic salmon was the best delivery route for inducing an antibody response against these antigens in this species. Even though IP injection did not induce an increase in antibody levels in the skin mucus, there was an increased systemic antibody response and an apparent increase of antibody production in mucosal tissues as demonstrated by the increased level of specific antibody levels in supernatants from the tissue explants.     

Cellular and humoral immune response of foals to vaccination with Corynebacterium equi.

Transformation of peripheral blood lymphocytes from pony foals vaccinated and subsequently infected with Corynebacterium equi was studied. Three foals were vaccinated on two occasions using a formalinized C. equi vaccine with aluminum hydroxide as an adjuvant. Three nonvaccinated foals served as controls. Foals were challenged intratracheally with 9 x 10(9) C. equi six weeks after the initial vaccination.Foals survived this infection for one to two weeks. Significant lymphocyte transformation in response to C. equi antigens was detected in two vaccinated foals at the third week after initial vaccination and in all vaccinated animals at the fifth week. No statistically significant transformation was seen in nonvaccinated foals before infection. Vaccinated and nonvaccinated foals showed responsive lymphocytes following challenge. Vaccination offered no obvious protection against experimental challenge but this failure was probably due to an excessive infective dose of organisms. Low levels of humoral antibodies were detected in some challenged foals. The pathological changes in the lungs of infected animals were comparable with, but more fulminating than, changes observed in the natural disease.     

Reliable ELISAs showing differences between resistant and susceptible lines in hens orally inoculated with Salmonella Enteritidis

Reliable ELISAs were investigated with the aim to select hen lines resistant to Salmonella Enteritidis and producing high levels of antibodies. In the first experiment, the relation between the humoral response and the bacteriological results was assessed on hens from the Y11 resistant line and the L2 susceptible line, orally inoculated with 10(8) CFU S. Enteritidis per animal. Anti-lipopolysaccharide (LPS) IgG titres were higher but the liver and spleen were less contaminated in hens from the Y11 line than in hens from the L2 line (p = 0.013, 0.031 and 0.026 respectively). In the second experiment, the hens were inoculated orally with 1.7 x 10(8) CFU S. Enteritidis per animal in order to select the ELISA methods showing the more significant differences. ELISAs were based on LPS, flagella, LPS from rough (LPS-R) and smooth strains (LPS-S) and detected IgG and IgM antibodies from sera and yolks. No between-line host response variation was observed in the yolk, with LPS-S and R antigens nor with anti-LPS IgM in the sera. Otherwise, significant differences were encountered between hen lines with the ELISAs performed on the sera detecting anti-LPS IgG, anti-flagella IgG or IgM (p = 0.017, 0.017 and p < 0.001 respectively). When comparing the kinetics of the selected ELISAs, the IgG antibodies against LPS detected between-line variations as early as 1 to 4 weeks pi, whereas with IgG against flagella, the differences were only detected at 1 and 2 weeks pi and with IgM against flagella, the differences were significant at 1, 2, 4 and 8 weeks pi. In conclusion, resistant hen lines producing higher levels of antibodies than the susceptible hen lines may be selected with these ELISAs.     

A COMPARISON OF COMMERCIAL MYCOPLASMA GALLISEPTICUM ANTIGENS IN THE RAPID SERUM AGGLUTINATION TEST

Twenty-three chickens, aged 9 weeks, were housed in contact with a similar group of chickens which were infected with M. gallisepticum. The onset and development of the serum agglutinin responses which were detected by 3 commercial antigens using rapid serum agglutination tests up to 20 weeks of age, differed greatly both between the infected and in-contact groups and, within the latter group, between the antigens. Few reactions, which were weak and transient, were detected in 2 similar groups of chickens, neither infected with M. gallisepticum but 1 vaccinated at 12 and 17 weeks of age with killed Pasteurella multocida oil adjuvant vaccine.     

Immune responses of immunocompetent and immunocompromised mice experimentally infected with Bartonella henselae

The aim of this study is to understand host immune responses in immunocompetent and immunocompromised mice against Bartonella henselae infection. BALB/c and nude (BALB/c nu/nu) mice were inoculated intraperitoneally with 10(8) colony forming units of B. henselae (Houston-1 strain). Blood, brain, liver, spleen, kidney and bone marrow samples were collected 0, 3, 7, 14, 21 and 28 days after infection and submitted to bacteriological, serological and genetical examinations. B. henselae was isolated only from the liver 3 days after infection. DNA of the inoculums was detected by polymerase chain reaction from blood, liver, and spleen samples collected from BALB/c and blood from nude mice 3 and 7 days after infection. No bacterial DNA was detected from both BALB/c and nude mice thereafter during 4 weeks observation periods. These results indicate that the T-cell may not participate in the effective elimination of the organisms from mice. In addition, western blot analysis revealed that the antigens of 27.3- and 31.5-kDa reacted with IgM antibodies from the blood of BALB/c and nude mice after 3 days of infection, suggesting that these antigens were recognized by thymus-independent mechanism. Furthermore the antigens were detected from the culture-supernatants of B. henselae, indicating that these antigens were secreted from the organisms.     

Immunoreactive protein antigens of Mycoplasma pulmonis in experimentally infected rats

Mycoplasma pulmonis was cultured in modified Hayflick's medium, washed in 0.25 M NaCl, and solubilized by 2.5% sodium dodecyl sulfate. Protein antigens of M pulmonis separated by polyacrylamide-gel electrophoresis were blotted onto nitrocellulose strips. Specific-pathogen-free rats were inoculated intranasally with M pulmonis. The serum samples of these rats were obtained periodically and used to react with fractionated M pulmonis antigens which were fixed on the nitrocellulose strips. The antigen-antibody reactions were further recognized by 125I-labeled antiglobulin. Detection of immunoreactive antigens was obtained by autoradiography. Antibody response was not detected in serum obtained 7 days after rats were inoculated, and by 14 days, a slight response to several proteins was found. At 28 days after rats were inoculated, many immunoreactive antigens were detected. Generally, antibodies against antigens of moderate to low molecular weight appeared early in the infection, and antibodies against antigens of high molecular weight appeared late. Important immunoreactive antigens thus identified can readily be distinguished from more than 58 different M pulmonis antigens detectable by sodium dodecyl sulfate polyacrylamide-gel electrophoresis. The humoral antibody response was measured by an enzyme-linked immunosorbent assay. The immunoglobulin G antibodies were initially detected at low level at 7 days after rats were inoculated. These humoral antibody responses reached maximum by 28 days. The increase in serum antibody titer corresponded with numbers of immunoreactive antigens detected by immunoradio-binding assay. The information gained by this investigation may improve our understanding of the antigenicity of M pulmonis and the immune response of rats exposed to M pulmonis.     

Effect of calf age and Salmonella bacterin type on ability to produce immunoglobulins directed against Salmonella whole cells or lipopolysaccharide.

A commercially available Salmonella bacterin was administered to Holstein calves starting at 1 to 19 weeks of age. Serum samples were obtained before administering bacterin and at 2-week intervals thereafter. An ELISA with Salmonella dublin lipopolysaccharide (LPS) or S dublin whole cells as antigen, was used to measure specific IgG and IgM responses. Antibody responses to LPS were not detected from calves < 12 weeks old inoculated with killed bacterin. Immunoglobulin responses to whole-cell antigen were detected from all age groups of calves inoculated with the same killed Salmonella bacterin. Calves < 11 weeks old are able to produce immunoglobulins to some whole-cell antigens, but are unable to produce anti-LPS immunoglobulins when inoculated with killed Salmonella bacterin. This age-related response to killed Salmonella antigens may account, in part, for increased susceptibility to salmonellosis in calves < 12 weeks old. In comparison to the response for killed antigen, 8 calves given modified-live aromatic-dependent S dublin bacterin at 1 to 3 weeks of age had detectable anti-LPS immunoglobulins after immunization, although the response was not as rapid and was of a lesser magnitude than that of older calves given killed Salmonella bacterin.     

Detection of Sarcocystis antigens in the sera of experimentally-infected pigs and mice by an immunoenzymatic assay

Immunoglobulins raised against Sarcocystis miescheriana and Sarcocystis muris cystozoite antigens were isolated from rabbit immune sera by affinity chromatography (using CNBr-activated Sepharose 4B for antigen immobilization). The specific immunoglobulins were incorporated into double-antibody sandwich immuno-enzymatic assays which were firstly quantitated and then used to detect soluble Sarcocystis antigens in the sera of experimentally-infected pigs and mice. Assays employing immunoglobulins attached to the solid-phase at concentrations of 80 micrograms/ml were capable of detecting homologous soluble cystozoite and sporozoite reference antigens at concentrations as low as 8 micrograms/ml. Circulating antigens were detected both in the presence and absence of acute clinical disease in pigs experimentally-infected with high and low doses of S. miescheriana sporocysts. The antigenemia detected was transitory (occurring from 3-20 days post-inoculation: dpi) and coincided well with the sporozoite and merozoite phases of parasite development. Circulating antigens were also detected during subclinical infections in mice (from 4-49 dpi) following their experimental infection with low doses of S. muris sporocysts. Specific immuno-enzymatic assays for circulating Sarcocystis antigens may therefore prove useful in the clinical diagnosis of acute sarcocystosis.     

Antibody responses against avian reovirus nonstructural protein sigmaNS in experimentally virus-infected chickens monitored by a monoclonal antibody capture enzyme-linked immunosorbent assay

Crude antigen preparations from avian reovirus (ARV)-infected chicken embryo fibroblasts (sigmaNS) or from bacterially expressed protein sigmaNS (esigmaNS) were captured by monoclonal antibody 1E1(MAb 1E1) against ARV nonstructural protein sigmaNS immobilized on the ELISA plates and were used as the MAb capture ELISA for antibody detection. Sixty one-week-old specific pathogenic free (SPF) chickens were divided into six groups and were vaccinated with live or inactivated ARV vaccine preparations in different combinations or inoculated with a virulent ARV strain. Sera collected from the birds were tested for their antibody responses to ARV nonstructural protein sigmaNS. Using the MAb capture ELISAs, the level of nonspecific binding reactions was tested on the serum samples obtained weekly from mock-infected SPF chickens from 1 to 25 weeks and compared to the results tested by the conventional ELISA. The results indicated that both MAb capture ELISAs had lower nonspecific bindings than those in the conventional ELISA, even in older birds. Antibody responses against ARV sigmaNS of the birds which received the inactivated vaccine twice (group I), inactivated vaccine followed by a live vaccine (group II), or a live vaccine followed by boosting with an inactivated vaccine (group III) were detected by MAb captured ELISA with sigmaNS crude antigens. The absorbance values increased rapidly at 1-2 weeks after boosting, approximated a peak at 5-6 weeks of age, and maintained this throughout the length of the experiment. The absorbance values of the MAb capture ELISA showed a good correlation to the SN titers ( r value > 0.85). On the other hand, serum samples from the birds which received the live vaccine twice (group IV) or were inoculated with a virulent ARV (group V) did not show antibody responses to sigmaNS, similar to those from the mock-infected birds (group VI), as the absorbance values maintained at a low level (below 0.5) throughout the length of the experiment. Similar results were obtained in the sera detected by MAb capture ELISA with crude esigmaNS antigens, except that the absorbance values in the sera from the birds in group III were gradually increased and later approximated a peak at 11 weeks of age and maintained this throughout the length of the experiments. The results suggest that MAb capture ELISAs can be readily used to detect antibody responses of the birds against ARV nonstructural protein sigmaNS which may reflect an immune status of a chicken flock, receiving ARV vaccine as long as including an inactivated vaccine.     

Enzyme-linked immunosorbent assay to detect subgroup-specific antibodies to avian leukosis viruses

An enzyme-linked immunosorbent assay (ELISA) was developed to detect antibodies against avian leukosis viruses (ALV), using antigens extracted from Rous-associated virus-inoculated chicken embryo fibroblast (CEF) cells by Nonidet P-40 treatments. The antigens reacted strongly to sera of chickens immunized with antigenically homologous viruses, but weakly to those of chickens immunized with heterologous viruses. Antigens extracted from noninoculated CEF cells by the same procedures did not react to either of the immune sera. Normal control sera did not react to any of the antigens. Reactivities of immune sera were decreased markedly by the sera adsorbing with homologous Rous-associated virus-inoculated CEF cells, but not with heterologous CEF cells. The ELISA-specific optimal doses (the differences between the optimal doses with antigens from ALV-inoculated and noninoculated CEF cells) were correlated strongly with the virus-neutralization titers (r = 0.876, P less than 0.01). Examination of the antibody response from ALV-inoculated chickens revealed that ELISA detected antibodies at the same time or several weeks earlier than did the virus-neutralization test.     

The humoral immune response of lambs experimentally infected with Mycoplasma ovipneumoniae

Using sera from lambs experimentally infected with Mycoplasma ovipneumoniae and Pasteurella haemolytica, the development of a good humoral immune response to M. ovipneumoniae was detected by ELISA. The antibody titres peaked 41 days post-infection and good antibody titres were maintained over the 16-week experimental period. Immunoblotting revealed that antibodies to specific antigens appeared in the sera in a sequential manner, some being seen shortly after infection and others developing only after a substantial time lag. Antibodies were raised against almost all the major antigens detected in one laboratory strain (956/2) and against all antigens previously shown to be conserved in 22 Scottish field isolates of M. ovipneumoniae.     

Use of monoclonal antibodies for detecting T brucei brucei infection in splenectomised dogs

A monoclonal antibody against a plasma membrane antigen of Trypanosoma rhodesiense was used for the detection of T brucei group-specific circulating antigen in 24 adult local dogs experimentally infected with T brucei brucei strain 8/18. Ten of the dogs were splenectomised and the remainder non-splenectomised (intact). Five dogs each from the splenectomised and intact groups were inoculated intravenously with try-panosomes. The infected dogs developed trypanosomiasis between days 4 and 8 after infection. The circulating antigens were detected as early as six days after infection and remained high until two weeks after treatment, when the circulating antigen declined. The detection of the antigens showed the existence of infection unlike the antibody test. The treatment of the infected dogs with diminazene aceturate (Berenil; Hoechst) at a dose of 7-0 mg/kg on day 21 after infection cleared all the parasites but elevated the circulating antigen levels. The antigen capture enzyme-linked immunosorbent assay is a useful diagnostic tool for complementing parasitological diagnosis, for detecting infection in the field and for ascertaining the efficacy of trypanocidal drugs.