Gross and Histopathological Findings of Naturally Occurring Anaplasma marginale Infection in Cattle

Background: Bovine anaplasmosis is a haemolytic disease of cattle caused by an obligate intra-erythrocytic bacterium Anaplasma marginale and is characterized by high fever, dyspnoea, anaemia, icterus, decreased milk production and death. The present study was undertaken to study the gross and histopathological changes caused by naturally occurring A. marginale infection in cattle. Methods: History and clinical examination of animals revealed inappetance/anorexia, presence of tick infestation, high fever, pale or icteric mucous membranes, tachycardia, dyspnoea and lymphadenomegaly. The diagnosis of A. marginale infection was done by blood smear examination and further confirmed by polymerase chain reaction and sequencing analysis. During the present study, two animals did not respond to treatment and were succumbed to A. marginale infection. A systematic post-mortem examination was performed on the animals and gross lesions were recorded. The tissue samples from various vital organs such as heart, lungs, liver, spleen and kidneys were collected in 10% neutral buffered formalin and processed for histopathological examination. Result: The post-mortem examination revealed emaciated carcass with yellowish discoloration of serosal surfaces of the abdominal organs, haemorrhagic heart, congestion of lungs, hepatomegaly, distension of the gallbladder and splenomegaly. The major histopathological changes noticed included myocardial degeneration and necrosis, interstitial pneumonic changes, degenerative changes in hepatocytes and renal tubular epithelial cells, enlargement of red pulp area of spleen with histiocytic proliferation and hemosiderosis. Histopathology also revealed inflammatory process characterized by infiltration of mononuclear cells in various organs. Very few reports are available on the pathological aspects of A. marginale infection and thus the outcome of the present study can yield valuable information to aid in the diagnosis of bovine anaplasmosis under field conditions.

THE EFFICACY OF OXYTETRACYCLINE THERAPY AND THE DURATION OF TREATMENT IN THE COURSE OF BOVINE ANAPLASMOSIS

A total of 27 crossbred calves (12 intacts, 9 splenec­tomised and 6 uninfected control) were sub­cutaneously Inoculated with 2 x 107 Anaplasma marginale infected erythrocytes. Oxytetracycline (at 10mg/kg body weight) was administered in­travenously when the PCV dropped to 16 per cent or below. The pattern of development of parasitaemia, appeared to be similar in both intact and splenec­tomised calves. The spelectomised calves, however, gave higher percentage of parasitaemia. Fluctuation in the PCV followed the same pattern in both groups, but the splenectomised calves were observed to suffer more anaemic crisis than the intact ones. In the intact calves, all those treated once and for 2 consecutive days survived. In the splenectomised calves, all those treated once died, while all those treated for 2 consecutive days survived. It may be concluded that, 2 consecutive ox­ytetracycline treatments (at 10mg/kg body weight) gave better recovery rates in cases of clinical bovine anaplasmosis.

Bovine Anaplasmosis and Control

Bovine anaplasmosis is one of the most important tick borne diseases of ruminants worldwide causing significant economic losses in the livestock industries due to the high morbidity and mortality in susceptible cattle herds. Bovine anaplasmosis, caused by Anaplasma marginale, is an infectious but non-contagious disease. The mode of transmission of bovine anaplasmosis includes mechanical (blood contaminated fomites (needles, ear tagging, dehorning and castration equipment), biological (tick bites) and transplacental (mother to fetus). Bovine Anaplasmosis occurs in tropical and subtropical regions worldwide. Cattle of all ages are susceptible to infection with A. marginale, but the severity of disease increases with age. The common clinical sign of bovine anaplsmosis includes; fever, anorexia, rapid loss of body condition, severe decrease in milk production, pale and icteric mucous membranes, increased heart and respiratory rates, muscle weakness and depression. Diagnosis of bovine anaplasmosis can be made by demonstration of A. marginale on stained blood smears from clinically infected animals during the acute phase of the disease, but it is not reliable for detecting infection in pre-symptomatic or carrier animals. Instead, serological demonstration of antibodies and confirmation of antigen with molecular detection tools are used for diagnosis. Anaplasmosis can be treated by administration of oxytetracyclines, however oxytetracyclines do not clear the parasite from carrier animals. Control measures for bovine anaplasmosis vary with geographical location and include maintenance of Anaplasma free herds, vector control, administration of antibiotics and vaccination. Intensive acaridae application to control ticks has a number of limitations, therefore, immunization together with strategic tick control is recommended for exotic and crossbred cattle. Further studies on epidemiology of bovine anaplasmosis is needed

Immunoinformatic Analysis to Identify Proteins to Be Used as Potential Targets to Control Bovine Anaplasmosis

Omics sciences and new technologies to sequence full genomes provide valuable data that are revealed only after detailed bioinformatic analysis is performed. In this work, we analyzed the genomes of seven Mexican Anaplasma marginale strains and the data from a transcriptome analysis of the tick Rhipicephalus microplus. The aim of this analysis was to identify protein sequences with predicted features to be used as potential targets to control the bacteria or tick-vector transmission. We chose three amino acid sequences different to all proteins previously reported in A. marginale that have been used as potential vaccine candidates, and also, we report, for the first time, the presence of a peroxinectin protein sequence in the transcriptome of R. microplus, a protein associated with the immune response of ticks. The bioinformatics analyses revealed the presence of B-cell epitopes in all the amino acid sequences chosen, which opens the way for their likely use as single or arranged peptides to develop new strategies for the control and prevention of bovine anaplasmosis transmitted by ticks.

High prevalence of Anaplasma marginale in the Crioula Lageana cattle

Introduction: Bovine anaplasmosis is caused by the bacterium Anaplasma marginale; its transmission occurs through vectors such as ticks. Crioula Lageana is a native cattle breed from the South of Brazil used for beef production, with excellent meat quality. There are no studies of the epidemiology of this disease in Crioula Lageana even though tick damage is known to be frequent. Methodology: Blood samples were collected from 311 Crioula Lageana cattle and subjected to DNA extraction and polymerase chain reaction (PCR) using specific primers for the Major Surface Protein 5 (msp5) gene for the detection of the bovine anaplasmosis agent. The animals were classified according to the gender, the category and the presence or absence of ticks at the time of collection. The animal owners completed an epidemiological questionnaire to determine factors that might be associated with anaplasma infection. Results: The prevalence of A. marginale was 79.9%. The following factors were found to be protective against infection: I) the breeding objectives (whether animals were destined for beef production and trade or solely for beef production), II) tick control rate; and III) pregnant and lactating cows and calves as the categories least affected by the hemoparasite. The main risk factor for hemoparasite acquisition was the use of organophosphates and avermectins as acaricides. Conclusions: Crioula Lageana cattle are in a situation of enzootic stability, with a high prevalence of A. marginale infection. The factors associated with the infection were: I) breeding objectives, II) tick control rate, III) the acaricides used, and IV) the most tick-parasitized categories of cattle.