The overall incidence of canine monocytic ehrlichiosis was 3.26% in and around the Navsari district whereas hospital based incidence among the suspected cases was found 49.28% (34/69). The result was in accordance with
Senthil et al., (2020) who also reported an overall incidence of ehrlichiosis in 36% and 56.43% cases of dogs, respectively. On the contrary, a higher incidence of CME was detected by
Bhadesiya and Raval (2015) and
Kottadamane et al., (2017) in 62.07% and 86.90% of the dogs, respectively might be due to the large size of the population studied. While very low prevalence (1.33% and 0.63%) of
E.
canis in cases in dogs was reported by
Roopali et al., (2019) and
Prajapati et al., (2023), respectively. The variation in the incidence rate of CME might be attributed to distribution of the vector, geographical area, climatic condition, sample size and time of the sample collection
(Selim et al., 2020). Among 69 suspected cases, 34 (Thirty-four) dogs were found positive Anigen Rapid CaniV-4(Leish) test and 15.94% (11) dogs were found positive for
Ehrlichia genus using primers of 16S rRNA gene which produced an amplicon at 345 bp (Fig 3). Similarly,
Sarawade et al., (2023) also found 16.66% dogs positive for
E.
canis among 60 suspected dogs. The 72.5 per cent of dogs were found positive for antibodies to
E.
canis. The serological prevalence for CME found in our study was similar to the findings of
Sosa-Gutierrez et al., (2013) who reported 74.5% cases positive for
E.
canis antibodies using the IDEXX snap 4Dx test.
However,
Roopali et al., (2020) and
Van Hai and Khuong, (2021) detected
E.
canis antibodies in 100% and 95.7% cases, respectively through a dot-ELISA kit. The difference in sero-prevalence might be due to regional variations, different climates, sample sizes, sampling periods, methodology and the differences in the dog populations (outdoor, indoor, stray, or owned dog)
(Cetinkaya et al., 2016). This rapid test detects IgM produced by the body against the ehrlichial organism, hence, the presence of adaptive immunity suggests the presence of acute infection. Therefore, the dogs were found positive in rapid antibody tests and if showing clinical signs and other defined laboratory findings, then such dogs might be infected with
E.
canis infection. Further, a low number of
E.
canis infections detected using PCR technique might be due to
E.
canis being captured in tissues such as bone marrow and spleen resulting in low concentrations of DNA of organism in systemic circulation which was inadequate for PCR amplification
(Cetinkaya et al., 2016). Looking at the literature, it was found that Nested PCR is a more efficient technique in the detection of CME rather than conventional PCR because Nested PCR is a modification of conventional PCR which increases the specificity of any reaction. Besides this,
Kalaivanan et al., (2020) stated that any previous treatment of the clinically suspected cases and prevalence of transmitting ticks in local regions could also be a cause for the variation in the results of
Ehrlichia canis detection using various techniques.
In the current study, tick infestation was noticed in 23 (67.65%) dogs which were found positive for CME and the significant (p<0.05) difference was observed between the tick-infested and non-infected dogs (Table 2). Moreover, the relative risk of owning ticks on the body was found >1
(Carneiro, 2011) in the present study which suggests that harbouring the ticks is relatively more prone to be affected by CME.
Game et al., (2019); Rao et al., (2020) and
Singh et al., (2021) also reported similar results in their studies.
Hematological alterations in ehrlichia affected dogs
There was a significant (p≤0.05) decrease in Hb level, TEC count and PCV in the infected dogs on the day of presentation compared to healthy dogs. These results suggested anemia in dogs infected with CME. The results of the present studies were in accordance with
Dhavalagi et al., (2021b) and
Singh et al., (2021). Anaemia found in dogs with CME could be due to loss of blood on account of thrombocytopaenia and immune-mediated destruction of red blood cells as well as suppression in production of colony forming erythroid cells resulting in decreased RBC production under the effect of bone marrow suppression by
Ehrlichia organism
(Game et al., 2019).
The platelet count of CME-infected dogs of the present study was significantly (
p≤0.01) decreased in comparison with healthy dogs. The thrombocytopaenia in
Ehrlichia infected dogs corroborates with the earlier reports of
Dhavalagi et al., (2021b) and
Singh et al., (2021). Thrombocytopaenia in CME might be observed due to decreased platelet production by bone marrow, increased platelet destruction and the presence of antiplatelet antibodies reduces adhesiveness of platelets because of immune-mediated response stimulated by
Ehrlichia organism. Besides, platelet consumption was increased and inversely platelet half-life was decreased due to immune-mediated splenic sequestration
(Dhavalagi et al., 2021b).
The mean TLC count of CME-infected dogs significantly (
p≤0.01) decreased when compared with healthy control dogs.
Game et al., (2019) also similarly reported leucopenia in their studies. While
Rao et al., (2020) and
Singh et al., (2021) observed leucocytosis in ehrlichiosis infected dogs as result of a hypersensitized immune system in the acute phase of infection. The variation in the same parameters among the authors could be associated with the presentation of dogs in various stages of CME (acute, sub-clinical and chronic) during blood sample collection. It has been reported that in the acute or subclinical phase there will be leucocytosis as a result of body defence whereas leukopenia is observed in chronic stage due to myelosuppression
(Rao et al., 2020).
Biochemical alterations in ehrlichia affected dogs
The elevation of total protein value could be due to either dehydration or increased gamma globulin response after
Ehrlichia organism infection
(Smitha and Vijayakumar, 2014). Similar findings were alsonoted by
Mondal et al., (2019). Further, the albumin value was significantly
(p≤0.01) lower in CME-infected dogs than in healthy control dogs. This finding was in accordance with the study of
(Smitha and Vijayakumar, 2014);
Dhavalagi et al., (2021a) and
Singh et al., (2021). The hypoalbuminemia in CME-infected dogs might be due to anorexia and reduced protein intake, loss of protein into the oedematous inflammatory fluid as a result of vasculitis which increases vascular permeability as well as protein excretion in urine because of glomerulopathy, or decreased production of protein due to liver damage in some cases
(Smitha and Vijayakumar, 2014) (Dhavalagi et al., 2021a).
In the present study, SGPT was non-significantly higher in CME-infected dogs as compared to healthy control dogs. This was in agreement with the earlier reports of
Singh et al., (2021). Besides,
Dhavalagi et al., (2021a) reported significantly higher levels of SGPT in
Ehrlichia-infected dogs. Additionally, the SGOT values were found non-significantly higher in CME-infected dogs as compared to healthy control dogs. This finding was in accordance with
Parashar et al., (2015) who also reported same results.
The ALP value was significantly (p≤0.01) higher in CME-infected dogs of the present study in comparison with healthy control.
(Smitha and Vijayakumar, 2014);
Dhavalagi et al., (2021a) and
Singh et al., (2021) also reported the same results in their study. Hepatocytes were compressed and injured by development of many expanding foci of reticuloendothelial cells in the hepatic sinusoids which compressed the function of hepatocytes leading to their necrosis and rise in the levels of serum SGPT, SGOT and ALP but this might be found for transient period, hence, the liver associated enzymes could not significantly altered in all the presented cases
(Smitha and Vijayakumar, 2014). Further, infiltration of perivascular mononuclear cells because of hepato-biliary dysfunction might also contribute to the elevation of these enzymes
(Nair et al., 2016).
The elevated values of BUN and creatinine found in the present study were similar to
Rao et al., (2020) and
Singh et al., (2021) but in contrast with the study of
Kottadamane et al., (2017) and
Mondal et al., (2019) who noted non-significantly increased value of BUN in CME infected dogs. The increased creatinine and BUN values in ehrlichiosis infected dogs might be due to immune complex-mediated glomerulonephritis which affect the GFR of nephron and resulted into renal pathology
(Roopali et al., 2018).
A significant improvement towards normalcy was observed in platelet count, TLC and blood glucose before and after treatment values in both the treatment groups (Table 3). Likewise, a significant regression was also observed in albumin, ALP, BUN and Creatinine values while comparing before and after treatment data of both the treatment groups (Table 4). However, looking at Table 5, a significant percentage of reduction was observed in the clinical score of group III CME-affected dogs than group II after 14 days of treatment. The better efficacy of imidocarb was reported by
Xaxa and Kumar, (2018),
Roopali et al., (2018) and
Game et al., (2020) which was similar to the present study. In contrary to present findings,
Rao et al., (2022) stated that doxycycline was far greater in the normalcy of clinical signs in comparison with imidocarb, whereas
Sainz et al., (2000) reported equal efficacy of both the drugs in returned to normal clinical signs. The better efficacy of imidocarb recorded in the present study might be due to the persistence of the drug for a longer period in plasma and tissue and therefore produces highly active concentration to destroy the intracellular
Ehrlichia organism
(Game et al., 2020).
