Haemonchus contortus is a nematode that infects small ruminants. It releases a variety of molecules, designated excretory/secretory products (ESP), into the host. Although the composition of ESP is largely unknown, it is a source of potential vaccine components because ESP are able to induce up to 90% protection in sheep. We used proteomic tools to analyze ESP proteins and determined the recognition of these individual proteins by hyperimmune sera. Following two-dimensional electrophoresis of ESP, matrix-assisted laser desorption ionization time-of-flight and liquid chromatographytandem mass spectrometry were used for protein identification. Few sequences of H. contortus have been determined. Therefore, the data base of expressed sequence tags (dbEST) and a data base consisting of contigs from Haemonchus ESTs were also consulted for identification. Approximately 200 individual spots were observed in the two-dimensional gel. Comprehensive proteomics analysis, combined with bioinformatic search tools, identified 107 proteins in 102 spots. The data include known as well as novel proteins such as serine, metallo-and aspartyl proteases, in addition to H. contortus ESP components like Hc24, Hc40, Hc15, and apical gut GA1 proteins. Novel proteins were identified from matches with H. contortus ESTs displaying high similarity with proteins like cyclophilins, nucleoside diphosphate kinase, OV39 antigen, and undescribed homologues of Caenorhabditis elegans. Of special note is the finding of microsomal peptidase H11, a vaccine candidate previously regarded as a "hidden antigen" because it was not found in ESP. Extensive sequence variation is present in the abundant Hc15 proteins. The Hc15 isoforms are differentially recognized by hyperimmune sera, pointing to a possible specific role of Hc15 in the infectious process and/or in immune evasion. This concept and the identification of multiple novel immune-recognized components in ESP should assist future vaccine development strategies.

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Two excretory secretory (ES) antigens of adult Haemonchus contortus with molecular weights of 15 and 24 kDa, respectively, were evaluated as protective immunogen against haemonchosis. Sheep were vaccinated three times and subsequently challenged with 20,000 infective larvae. Vaccination induced significant reduction (> 70%) in mean faecal egg counts and abomasal worm burden compared to the non-vaccinated control group or adjuvant control group. Vaccination induced ES-specific antibodies and stimulated infiltration of mast cells in the abomasal tissue.

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Canine monocytic ehrlichiosis (CME) is a potentially fatal tick-borne disease caused by the rickettsia Ehrlichia canis (16). The etiologic agent was first recognized in Algeria in 1935 (8). Since then, it has been reported worldwide, causing extensive morbidity and mortality among domestic dogs and other canids (11, 28, 51). The principal vector of CME is Rhipicephalus sanguineus (11). Recently, it has been shown experimentally that Dermacentor variabilis is also capable of transmitting E. canis (24). The pathogenesis of CME consists of an incubation period of 8 to 20 days, followed sequentially by acute, subclinical, and in some cases chronic phases. The disease may be manifested by a wide variety of clinical signs of which depression, lethargy, weight loss, anorexia, pyrexia, lymphadenomegaly, splenomegaly, and bleeding tendencies are the most common. Principal hematologic abnormalities include thrombocytopenia, mild anemia and mild leukopenia during the acute stage, mild thrombocytopenia in the subclinical stage, and pancytopenia in the severe chronic stage. The main biochemical abnormalities include hypoalbuminemia, hyperglobulinemia, and hypergammaglobulinemia (16). CME has been researched extensively in the last decade, and special efforts have been made to elucidate the pathogenesis of the disease. Better understanding of major mechanisms involved in the pathogenesis of the disease may assist clinicians in understanding the disease process and providing appropriate treatment, affording a better prognosis to their patients. In the light of the recent emergence of similar ehrlichial pathogens that infect human patients, the understanding of pathogenic processes in CME may contribute to the understanding of human monocytic ehrlichiosis and human granulocytic ehrlichiosis. This article reviews recent investigations in the pathogenesis of CME with special reference to platelet disorders and serum protein alterations, the principal hematological and biochemical abnormalities in CME, respectively. Host immune response in both acute and persistent E. canis infection is discussed and is proposed to be involved in the pathogenesis of disease manifestations.