Blood smear examination is considered as gold standard for diagnosis of trypanosomosis even after its limited sensitivity. Although this method is easy to conduct without using expensive equipments. This method gives positive results if numbers of trypanosomes are 105 or more in one ml of blood (Reid et al. 2001). The another method having highest sensitivity to detect trypanosomes is amplification of parasite DNA using PCR (Agrawal et al. 2018). The study revealed that lower the level of glucose either by portable blood glucose meter or semi auto analyzer increase the chance of trypanosomosis.
Among 123 buffaloes having history of fever, 21 buffaloes found positive for trypanosomosis in PCR based diagnosis. The blood glucose level of all the infected animals found subnormal with average value of blood glucose by portable glucometer and colorimetric methods was 32.32 ± 9.76mg/dl and 35.77 ± 10.67mg/dl. Precision and accuracy of portable glucometer for cattle was documented 95% and 92%, respectively and value for portable glucometer was significantly lower by 8.3% in cattle (Katsoulos et al. 2011). Hypoglycaemia was reported in infected buffalo which occurs due to increase demand of glucose for metabolism of Trypanosoma (Takeet and Fagbemi 2009). Simultaneously motility of T. evansi depends upon the availability of glucose (Marshall 1948; Newton 1978) besides this high fever and hepatocellular damage in host is also responsible for enhanced metabolic rate. This is in corroborated with finding of Sazmand et al. (2011). There is difference in glycolysis for glucose metabolism between T. evansi and eukaryotes because end product is pyruvate rather than lactate in glucose metabolism of T. evansi (Opperdoes 1987). Glycolysis is efficient energy pathway as conversion of D-glyceraldehyde-3-phosphate (DGAP) to pyruvate yields two ATP molecules and Triosephosphate isomerase (TIM) (Hunt, 2010). End product of glucose by T .evansi is pyruvate (Marshall 1948), although it is utilized by host tissue but accumulation in blood is directly proportional to number of T. evansi. Hence, if high number of T. evansi is there then resulting in to high concentration of pyruvate leading to depletion of alkalosis resulting in acidosis. Resultant of acidosis is the less affinity of hemoglobin with oxygen (Newton 1978) reflected clinically in form of respiratory distress as reported open mouth breathing in infected buffalo. The average value of glucose, haemoglobin was lower in trypanosome positive animals detected by PCR than microscopy detected trypanosomsa positive buffaloes. The normal value of glucose under field condition in buffaloes was reported 57.66 ± 0.949 and no significant difference (P < 0.05) in blood glucose levels among buffaloes of different categories of farmers viz Landless, Marginal, Small and Large categories of farmers (Maurya and Singh 2015).
All the PCR positive cases of present study had significantly lower value of haemoglobin (8.605 ± 0.34). In trypanosomosis, decrease in haemoglobin and PCV are hallmark pathological changes in various species of animals (Tabel et al. 1978). In bovine trypanosomosis anaemia is occurred mainly due to haemolytic factors like hemolysis and free fatty acids, immunologic mechanisms, hemodilution, coagulation disorders, depression of erythrogenesis and release of trypanosomal sialidase (Omer et al. 2007; Adamu et al. 2008). Due to activated and elevated mononuclear phagocytic system, erthrophagocytosis occur along with significant reduced half- life of erythrocytes (Adamu et al. 2008). Besides, sialic acid on surface of erythrocytes are cleaved by sialidase and exposed galactosyl residue recognized by D-galactose specific lectins on macrophages resulting in to erthrophagocytosis (Sallau et al. 2008) otherwise removal of sialic acid from the erythrocyte surface is normally an age-dependent process leads to phagocytosis of aged cell (Sallau et al. 2008). Murthy, 1980 reported normal range of Hb in Indian buffaloes was 10.3 ± 0.2g/dl. Agrawal et al. 2020 reported 90.48% of Trypanosoma infected buffalo was showing anaemic condition. Hypoglycemic condition in buffaloes need to be differentiated from ketosis. Buffaloes in type I ketosis(occurs at 4–6 weeks after parturition) and type II ketosis (Very early lactation) showed hypoglycemia without hyperthermia and anaemia (Herdt 2019). Babesiosis and theileriosis are other haemoprotozoan diseases in which if hypoglycaemia is occurred but the degree of hypoglycemia; (Theilerioisis; 51.9 ± 3.82mg/dl), (Babesiosis; 56.67 ± 1.87 mg/dl) is less than in trypanosomosis (35.77 ± 10.67mg/dl) (Ganguly et al. 2019).
Needless to say that timely and accurate diagnosis of trypanosomosis would be helpful to minimize the menace of drug resistance (Chitanga et al 2011) and problems is exaggerated by the facts that research for development of new trypanocide drugs has not been occurred from decades. Resistance against trypanocidal drugs have been reported from 21 African countries along with multiple drug resistance from 10 African countries leading to lesser therapeutic option and major impact on economy. Due to slowdown in development of new antimicrobial (Grace, 2015), it is need of hour that limited chemoprophylactic and chemotherapeutic trypanocidal compounds should be used with caution (Barret 2004). Due to less cost benefit ratio, pharmaceutical companies are not interested to invest in development of new trypanocidal drug (Geerts et al 2010). Therefore timely and accurate diagnosis of trypanosomosis would be helpful for longevity of available trypanocidal drugs. Plethora of literature is available which clearly indicate that hypoglycemia and anemia is valuable feature of trypanosomosis. But till date no literature traced which indicate the use of theses parameter to diagnose the trypanosomosis in field conditions. The inference can be drawn from present study that if temperature is high and blood glucose level is low then such buffaloes should be suspected for trypanosomosis. Additionally further confirmation of trypanosomosis suspected buffaloes could be done in laboratory by estimating haemoglobin and blood smear examination in low resource laboratory in developing nations. Lower the blood glucose level in fevered animals may suspect the trypanosomosis. In these cases portable blood glucose meter may help the field veterinarian for on spot estimation of blood glucose level of fevered animals. An on spot estimation of lowered glucose level, anaemia and high temperature increases the probability of trypanosomosis. So that timely treatment of infected animal could be possible in rural area without wasting of time to get the report from full equipped laboratory.