Evaluation of clinical markers for diagnosis of bovine theileriosis--a study of 21 calves.
Theileria annulata, an apicomplex parasite is the causative agent of lymphoproliferative disease of cattle, tropical theileriosis that cause significant economic losses in large parts of Asia and Africa (Hassanpour et al., 2013; Woods et al., 2013). Theileria genus differentiates themselves from the Babesia parasites by having a schizont stage in their life cycle, which parasitized the host's white blood cells. Ticks of genus Hyalomma are common vectors of protozoan parasite that transmit parasite to final hosts including cattle and buffaloes. Like other parasites (such as Toxoplasma and Plasmodium sp.), the life cycle of Theileria is complex and involves several morphologically different stages. Sporozoite entry in target cells is a rapid process and within 15-30 minutes of invasion the infective sporozoite eliminates the enclosing host cell membrane and free in cytoplasm, parasite then differentiates into a multinucleated syncytium called a schizont.
The parasite acts as a serious constraint to cattle production in endemic areas, causing lethal infections in exotic cattle and considerable mortality in indigenous and crossbred stock (Nazifi et al., 2008; Branco et al., 2010). The bovine mortality rate rises up to 40-60% and even more (Razmi et al., 2009). An estimate stated that bovine tropical theileriosis costs the Indian livestock sector about US$384.3 million annually (Minjauw and McLeod, 2003). Calf mortality owing to theileriosis is one of the major impediments to the livestock upgrading programmes in Indian subcontinent (Godara et al., 2009; Sudan et al., 2012). Clinical manifestations of tropical theileriosis in newborn calves diverge from per-acute to acute or sub-acute to chronic. It mainly depends upon the damaging effect of pathogen on lymphoid tissues and susceptibility of host. A marked rise in body temperature, reaching 40-42[degrees]C, is followed by lethargy, lacrimation, nasal discharge, exophthalmia and swelling of superficial lymph nodes; hemolytic anemia is among the characteristic features of tropical theileriosis (Fartashvand et al., 2013; Singh et al., 2013). The portrayal of clinical manifestations of tropical theileriosis in naturally infected calves could be pivotal in facilitating a rational verdict to the veterinary clinicians in field conditions. Thus, in the current study we aimed to evaluate the clinical markers of natural T. annulata infection in calves.
Materials and Methods
21 naturally Theileria annulata infected indigenous and crossbred calves of either sex, aged between 15 to 60 days presented for clinical examination were evaluated for the study. Blood smear and lymph nodes aspirate smear examination was conducted by routine methods. Clinical examination of suffering calves was performed ardently and revealed clinical markers such as lymph nodes enlargement, pallor or jaundiced mucous membrane, reduces appetite, pyrexia, pica, coughing and respiratory distress, lacrimation, exophthalmia, petechiae, recumbency, sub-mandibular and/or ventral edema, melena, diarrhea and hemoglobinnuria were recorded.
Out of 21 presented calves, sixteen were crossbred and five were of Sahiwal breed. Of these, 19 calves were female and two were male. Lymph nodes aspirate smear examination revealed presence of schizonts in mononuclear cells of 90.48% (19/21) calves (Fig. 1A). While, blood smear examination revealed presence of only schizonts in mononuclear cells of 14.29% (3/ 21) calves and presence of only piroplasms in the RBCs of 42.86% (9/21) calves (Fig. 1B). Moreover, 14.29% (3/21) of calves were positive for the both piroplasms and schizonts in blood smear examination. The remaining 28.57% (6/21) calves were neither positive for piroplasms nor for schizonts in blood smear examination, but were positive for presence of schizonts in mononuclear cells of lymph nodes aspirate smear examination.
The percentages of clinical markers revealed by the infected calves are summarized in Table 1. Clinical manifestations of generalized lymph nodes enlargement (Fig. 2A-B), pallor mucous membrane (Fig. 3), reduced appetite and pyrexia reaching 40-42[degrees]C (Fig. 4), were revealed by more than 75% of the infected calves. While, clinical manifestations of pica, coughing and respiratory distress, lacrimation and exophthalmia (Fig. 5A-D) were revealed by more than 50% of the infected calves. Clinical manifestations of petechiae and/or ecchymoses on sclera (Fig. 6A), conjunctival mucous membrane, tongue (Fig. 6B) and ear pinna, lateral recumbency (Fig. 7A) and submandibular and/or ventral edema (Fig. 7B) were revealed by more than 25% of the infected calves. While, less than 25% of the infected calves revealed clinical manifestations of diarrhea, melena, haemoglobinuria and yellow mucous membrane.
The results of the current study clearly signify that lymph nodes enlargement, pallor mucous membrane, reduced appetite, marked rise in the body temperature and exophthalmia are among the most common clinical markers revealed by the calves naturally infected with T. annulata. Significant feature of the disease is anemia owing to overproduction of cytokines, immune-mediated hemolysis and reactive oxygen species (Nazifi et al., 2009; Saleh et al., 2012). Pallid mucous membranes are indicative of anemic state of the affected calves. The transforming schizont is not restricted by the confines of a parasitophorous vacuole and is in a perfect position to interfere with host cell signaling pathways that regulate cell proliferation and survival (Shiels et al., 2006). The schizont completely hijacks the regulation of infected leukocytes and inhibits the apoptosis of infected cells conferring their over proliferation and clonal expansion. It interacts with host cell microtubules to ensure its persistence within the host cell and thus maintenance of the transformed phenotype (Woods et al., 2013). By associating with the mitotic apparatus during mitosis and cytokinesis, the parasite secures the equal distribution of the schizont between the two new daughter cells (Hulliger et al., 1964). The ability of T. annulata to infect predominantly macrophages/monocytes and B-cells and to transform infected host cells, inducing uncontrolled proliferation and clonal expansion of the parasitized cell population results into the lymphoproliferative disease of cattle (Woods et al., 2013) and thus bestows generalized lymphadenopathy.
Cells infected with T. annulata also produce high levels of inflammatory eytokines, especially tumor necrosis factor alpha (TNF-[alpha]) (Brown et al., 1995). This cytokine is a potent inducer of all the major clinical symptoms of acute tropical theileriosis such as pyrexia, anaemia, anorexia, muscle wasting and necrosis (Graham et al., 2001). In addition, TNF-[alpha] has been implicated in mediating the ulcerative lesions associated with tropical theileriosis and in enhancing the proliferation of infected cells (Forsyth et al., 1999). Clinical manifestation of edema, proptosis and diplopia in thyroid associated ophthalmopathy are attributed to infiltration of lymphocytes and enlargement of extra-ocular muscle, accumulation of glycosaminoglycan (GAG) (Balazs and Koranyi, 2011). The activated lymphocytes have been shown to secrete several cytokines including TNF-[alpha], interleukin-1 and interferon gamma (IFN-[alpha]) which are able to express HLADR antigens and stimulate fibroblasts to proliferate, produce GAG and free oxygen radicals. The pathological changes observed in different organs and tissues of T. annulata infected animals are reported to be the results of proliferation of infected macrophages, while other clinical symptoms result from pro-inflammatory cytokines produced by these cells, mainly TNF-[alpha] (Branco et al., 2010; El-Deeb and lacob, 2012). Thus, it is quit possible that the parasitized lymphocytes could be infiltrating and proliferating in the extra-ocular muscle of infected cave and thus local overproduction of TNF-[alpha] is under operation, bestowing clinical manifestation of exophthalmia.
In conclusion, an ardent inspection of a diseased calf by the field Veterinarian considering these clinical markers could aid in the diagnosis of theileriosis in newborn calves. The consideration of generalized lymph nodes enlargement, pallor mucous membrane, pyrexia, pica, coughing and respiratory distress, lacrimation and exophthalmia as the major clinical markers might be pivotal in clinical diagnosis of theileriosis in the field conditions.
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Shanker K. Singh (1), Vikrant Sudan (2), Asheesh P. Singh and Brajesh K. Yadav
Department of Veterinary Clinical Medicine
College of Veterinary Science and Animal Husbandry
U.P. Pt. Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya
Evam Go Anusandhan Sansthan (DUVASU)
Mathura-281001 (Uttar Pradesh)
(1) Corresponding author Email: firstname.lastname@example.org
(2) Department of Parasitology
Table 1: The portrayal of clinical markers of bovine tropical theileriosis of 21 calves Clinical markers Recorded Number of calves percentage (%) revealed Lymph nodes enlargement 100 21/21 Pallor MM 90.48 19/21 Reduced appetite 90.48 19/21 Pyrexia (40-42[degrees]C) 85.71 18/21 Pica 66.67 14/21 Coughing and respiratory 66.67 14/21 distress Lacrimation 66.67 14/21 Exophthalmia 52.38 11/21 Petechiae and/or ecchymoses 47.62 10/21 Lateral Recumbency 38.10 08/21 Submandibular or Ventral 38.10 08/21 edema Diarrhea 14.29 03/21 Melena 9.52 02/21 Haemoglobinuria 9.52 02/21 Jaundice (yellow) MM 9.52 02/21
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|Title Annotation:||Clinical Article|
|Author:||Singh, Shanker K.; Sudan, Vikrant; Singh, Asheesh P.; Yadav, Brajesh K.|
|Date:||Jan 1, 2014|
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