Insights on clinical presentation, therapeutic response and prognosis of two cases of severe canine ehrlichiosis associated with gastrointestinal and renal changes - case report

[Perspetivas sobre a apresentação clínica, a resposta terapêutica e o prognóstico de dois casos de erliquiose canina grave associados a alterações gastrointestinais e renais - relato de caso]

ABSTRACT

Canine monocytic ehrlichiosis has been considered an important tick-borne disease. In recent years, there has been an increase in the number of infected dogs and deaths. For this reason, studies have been conducted in order to provide practical information to veterinarians about the diagnosis, treatment and prognosis of dogs with ehrlichiosis. This study provides information on clinical presentation, therapeutic response and prognosis of two cases of dogs kept in different environments (rural and urban areas) with ectoparasite infestation and positive for canine ehrlichiosis associated with gastrointestinal and renal alterations. It was concluded that ehrlichiosis is a complex parasitic disease with several clinical manifestations, and despite the use of different medications, the involvement of vital organs can complicate treatment and lead to the death of the animals.

Keywords:
changes; hemoparasites; tick-borne disease

RESUMO

A erliquiose monocítica canina tem sido considerada uma importante doença transmitida por carrapatos. Nos últimos anos, tem-se verificado um aumento do número de cães infectados e de óbitos. Por esse motivo, têm sido realizados estudos com o objetivo de fornecer informação prática aos médicos-veterinários sobre o diagnóstico, o tratamento e o prognóstico de cães com erliquiose. Este estudo apresenta informações sobre o quadro clínico, a resposta terapêutica e o prognóstico de dois casos de cães mantidos em ambientes distintos (meio rural e urbano), com infestação por ectoparasitas e resultado positivo para erliquiose canina, associada a alterações gastrointestinais e renais. Concluiu-se que a erliquiose é uma doença parasitária complexa, com diversas manifestações clínicas e que, apesar da utilização de diferentes medicamentos, o envolvimento de órgãos vitais pode complicar o tratamento e conduzir à morte dos animais.

Palavras-chave:
alterações; hemoparasitas; doença transmitida por carrapato

INTRODUCTION

Ehrlichiosis is an emerging zoonotic bacterial disease caused by rickettsiae of the family Anaplasmataceae, which are obligate intracellular Gram-negative pathogens transmitted by vectors that affect both animal and human health (Ganguly and Mukhopadhayay, 2008; Jafarbekloo et al., 2014; Aziz et al., 2022). Due to its distribution in different areas of the world, this disease is also recognized as canine hemorrhagic fever, canine typhus, tropical canine pancytopenia, tracker dog disease, and canine rickettsiosis (Beall et al., 2012; Kukreti et al., 2018).

Despite the diversity of Ehrlichia species that infect domestic and wild animals, Ehrlichia canis, E. ewingii, and E. chaffeensis are the most reported (Aziz et al., 2022). In Brazil, E. canis was first described in the 1970s in Minas Gerais and is still considered the main agent involved in monocytic ehrlichiosis in canine patients seeking clinical care in veterinary hospitals (Costa et al., 1973; Vieira et al., 2011). However, studies describe ehrlichiosis in dogs infected with E. ewingii in the southeastern region of the country (Oliveira et al., 2009).

Since its identification in Algeria in 1935 (Donatien and Lestoquard, 1935), the severity of the clinical signs of ehrlichiosis obtained prominence during the Vietnam War when the disease, considered epizootic, caused the death of military dogs (Huxsoll et al., 1970; Vieira et al., 2011). In recent years, Canine Monocytic Ehrlichiosis (CME) has become a potentially fatal disease, requiring rapid and accurate diagnosis to initiate appropriate treatment and achieve a favorable prognosis (Skotarczak, 2003).

Clinically, dogs infected by Ehrlichia can be asymptomatic; however, CME can manifest with mild symptoms such as fever, ocular discharge, anorexia, weight loss, dyspnea, and lymphadenopathy, progressing to severe clinical signs such as hemorrhages, hepatosplenomegaly, jaundice, renal, locomotor, neurological, and cardiac alterations (Mylonakis and Theodorou, 2017; Ramakant et al., 2020; Zanfagnini et al., 2024).

In recent years, studies have highlighted that dogs with ehrlichiosis may exhibit altered cytokine levels, leading to hematological changes (Cabrales et al., 2007; Cardoso et al., 2023). In recent years, CME has spread to regions previously considered free of the disease, such as northern China, temperate regions of India, and central and northern areas of the United States (Sainz et al., 2015; Aziz et al., 2022). In Brazil, studies conducted in different regions indicate that the prevalence of E. canis infection in dogs can range from 0.7% to over 70.0% (Vieira et al., 2011; Dantas-Torres et al., 2018).

Although the diagnosis of CME being considered challenging due to its various stages and clinical manifestations (Donatien and Lestoquard, 1935), veterinarians may request different parasitological, serological, and even molecular tests for diagnostic confirmation (Guedes et al., 2015), in addition to monitoring hematological alterations (Bhadesiya and Raval, 2015). Antibiotics have been widely used in combination with adjuvant drugs for treatment helping to reverse the clinical signs of the disease (Fourie et al. 2015). As CME has been considered an important tick-borne disease with worldwide distribution (Maggi and Krämer, 2019), coupled with the increase in the number of infected dogs and fatalities in Brazil in recent years (Dantas-Torres et al., 2018, Crivellenti et al., 2021), studies have been conducted to provide practical information and guidance for veterinarians on the diagnosis, treatment, and prevention of ehrlichiosis (Sainz et al., 2015). Therefore, the current study aims to provide information on the clinical presentation, therapeutic response, and prognosis of two cases of severe canine ehrlichiosis associated with inflammatory bowel diseases.

ETHICAL ASPECTS

The research was submitted to the Ethics Committee on Animal Use of the University and approved under the number 6973120522).

CASUISTRY

A 14-year-old female Poodle, weighing 4.5kg, with a history of vomiting, diarrhea, anorexia, and urinary incontinence. The animal had not eaten for three days and had experienced episodes of vomiting and foul-smelling, yellowish diarrhea for over a week. The patient, which lived in the urban area of Nossa Senhora da Glória (10° 13' 0'' S and 37° 25' 27'' W) in the semi-arid region of Sergipe, Northeast Brazil, had a history of tick infestation (Rhipicephalus sanguineus). The dog did not have access to the street, lived with other dogs in the household, and was fed both commercial dog food and homemade food. Its vaccinations were out of date, and her deworming protocol was overdue. The physical examination revealed a respiratory rate (RR) of 24 breaths per minute, heart rate (HR) of 140 beats per minute, body temperature of 36.1 °C, body condition score of 2 (on a scale of 1-9), capillary refill time (CRT) of more than 3 seconds, and skin turgor (ST) of more than 2 seconds. The ocular, oral, and genital mucous membranes were jaundiced, the popliteal lymph nodes were enlarged, and the patient exhibited dyspnea, ataxia, enophthalmos, keratitis, keratoconjunctivitis, uveitis, and bilateral blindness (Fig. 1a). Additionally, the skin was jaundiced (Fig. 1c), with pustules, petechiae, cutaneous ulcerations, alopecia (Fig. 1b), dull and brittle hair (Fig. 1d).

The complete blood count (CBC) revealed normocytic hypochromic anemia, with microcytic hypochromic erythrocytes, as well as anisocytosis, acanthocytosis, echinocytosis, and poikilocytosis. The erythrocyte count was 2.83 (x10^6/mm^3), hemoglobin was 6.2 (g%), hematocrit was 21 (%), mean corpuscular volume (MCV) was 74.20 (fL), and mean corpuscular hemoglobin concentration (MCHC) was 29.52 (%). Platelets were 189,000 (/mm^3), total leukocytes were 10,000 (/mm³), with band cells at 1 (%) and 100 (/mm^3), segmented neutrophils at 79 (%) and 7,900 (/mm³), eosinophils at 1 (%) and 100 (/mm^3), lymphocytes at 17 (%) and 1,700 (/mm³), and monocytes at 2 (%) and 200 (/mm³).

The serum biochemistry demonstrated urea at 135.63 (mg/dL), creatinine at 3.24 (mg/dL), aspartate aminotransferase (AST/TGO) at 73.12 (U/L), alanine aminotransferase (ALT/TGP) at 39.46 (U/L), total proteins at 9.38 (g/dL), albumin at 2.1 (g/dL), globulins at 7.28 (g/dL), and calcium at 11.22 (mg/dL). A blood smear from whole blood and capillaries at the ear tip revealed the presence of Ehrlichia sp. morulae infecting neutrophils (Fig. 2a and b). The serology using the SNAP® 4Dx® Plus test was positive for ehrlichiosis. The Wood's lamp examination of the patient's skin and hair showed luminescent aspects compatible with fungal infection. The coproparasitological analysis, skin scraping, Dual Path Platform test for Canine Visceral Leishmaniasis (DPP®-LVC), and serological tests for antibodies against Anaplasma phagocytophilum, Anaplasma platys, Borrelia burgdorferi, and Dirofilaria immitis were all negative.

Due to the patient's unfavorable prognosis, the owner opted to take it home for palliative care, where it died after 72 hours.

A 2-year-old female Poodle, weighing 6.0 kg, with a history of chronic vomiting and diarrhea. The animal had experienced episodes of vomiting for over a week and had been suffering from watery, brown-colored diarrhea for two days. The patient resided on a farm in the Caatinga biome, in the rural area of Nossa Senhora da Glória - SE (10° 13' 0'' S and 37° 25' 27'' W). The dog had a history of flea (Ctenocephalides felis felis) and tick (Rhipicephalus sanguineus) infestation (Fig. 1f and h), had access to wooded and pasture areas and lived with other dogs, cattle, sheep, pigs, chickens, and wild animals on the property. It was fed a combination of commercial dog food and homemade food. Its vaccinations were out of date, and the deworming protocol had not been updated for over a year. Due to the clinical condition, the owner reported having self-administered Ivermectin 1% at a dose of 1 mL per 50 kg of body weight via subcutaneous injection, 100 mL of boldo-do-chile (Peumus boldus) tea orally and giving the dog a bath with a mixture of salt and vinegar, none of which resulted in clinical improvement. On physical examination, the respiratory rate (RR) was 36 breaths per minute, heart rate (HR) was 92 beats per minute, body temperature was 38.5 °C, body condition score was 3 (on a scale of 1-9), capillary refill time (CRT) was less than 3 seconds, and skin turgor (ST) was more than 2 seconds. The mucous membranes were pale, the submandibular, prescapular, and popliteal lymph nodes were enlarged, and the dog exhibited dyspnea, conjunctivitis (Figure 1e), pustules, petechiae, alopecia, and dull, dirty, brittle hair (Fig. 1g), in addition to episodes of emesis and diarrhea.

The complete blood count (CBC) revealed mild normocytic normochromic anemia and reactive lymphocytes. The erythrocyte count was 5.33 (x10^6/mm^3), hemoglobin was 10.3 (g%), hematocrit was 32 (%), mean corpuscular volume (MCV) was 60.04 (fL), and mean corpuscular hemoglobin concentration (MCHC) was 32.19 (%). Platelets were 215,000 (/mm³), total leukocytes were 3,900 (/mm³), with band cells at 1 (%) and 39 (/mm³), segmented neutrophils at 63 (%) and 2,497 (/mm³), eosinophils at 3 (%) and 117 (/mm³), lymphocytes at 31 (%) and 1,209 (/mm³), and monocytes at 2 (%) and 78 (/mm³). The serum biochemistry exhibited urea at 47.33 (mg/dL), creatinine at 0.9 (mg/dL), aspartate aminotransferase (AST/TGO) at 67.69 (U/L), alanine aminotransferase (ALT/TGP) at 59.53 (U/L), alkaline phosphatase at 23.56 (U/L), total proteins at 17.47 (g/dL), albumin at 2.1 (g/dL), globulins at 15.37 (g/dL), calcium at 9.99 (mg/dL), and chloride at 103.8 (mEq/L). A blood smear from capillary blood collected from the ear tip identified the presence of Ehrlichia sp. morulae infecting monocytes (Fig. 2c). The SNAP® 4Dx® Plus immunological test was positive for ehrlichiosis. Tests using the Wood's lamp, fecal parasitological analysis, DPP®-LVC test, and serological tests for antibodies against Anaplasma phagocytophilum, Anaplasma platys, Borrelia burgdorferi, and Dirofilaria immitis were all negative.

Emergency treatment was initiated with Maropitant Citrate (1.0mL/10kg body weight/IV/single dose), fluid therapy with 0.9% sodium chloride (50mL/kg/hour/IV/single dose), and a vitamin-based hepatoprotector containing Acetyl DL-methionine, Choline Chloride, Vitamin B1, B2, B3, B5, B6, and Glucose (2mL/IV/single dose). The following medications were prescribed: Doxycycline (50mg/kg/BID/orally for 14 days), Metoclopramide (0.5mg/kg/TID/orally for 3 days), Credeli™ Lotilaner (225mg/orally/single dose), and Biofarm® Hepatoprotector (2mL/BID/IM for 5 days). After three days, the patient returned exhibiting polydipsia and vomiting, and despite the guarded prognosis, it demonstrated normal appetite and food intake. A repeated complete blood count (CBC) showed normocytic normochromic anemia and 1% metarubricytes, with erythrocytes at 4.48 (x10^6/mm^3), hemoglobin at 6 (g%), hematocrit at 28 (%), MCV at 52.50 (fL), MCHC at 32.13 (%), platelets at 168,000 (/mm³), total leukocytes at 4,100 (/mm³), with band cells at 3 (%) and 123 (/mm³), segmented neutrophils at 54 (%) and 2,214 (/mm³), eosinophils at 2 (%) and 82 (/mm³), lymphocytes at 35 (%) and 1,435 (/mm³), and monocytes at 6 (%) and 346 (/mm³). Another round of fluid therapy with Ringer's lactate (90mL/kg/2 hours/IV/single dose) was administered, and Doxycycline (50mg/kg/BID/orally for 11 days) and Hepatoprotector (2mL/BID/IM for 2 days) were continued. Additionally, Ondansetron Dihydrate Hydrochloride (1mg/kg/TID/orally for 3 days) and Fipronil (0.67mL/1 to 10kg/topical use in a single dose) were prescribed. Despite the guarded prognosis and modest clinical improvement, the patient died 20 days after the treatment ended.

Figure 1
Clinical changes observed in canine patients with CME. a and e) Ophthalmopathy; b and d) dermatological changes; c) jaundiced skin; f and h) ectoparasites; and g) opaque and brittle hair.

Figure 2
Morulas of Ehrlichia sp. (red arrow) detected in neutrophils (N) and monocytes (M) from canine patients.

DISCUSSION

This study presents information on the clinical manifestations, therapeutic response, and prognosis of severe canine ehrlichiosis associated with inflammatory diseases in vital organs in dogs kept in different environments (rural and urban area) in the Northeast region of Brazil.

In recent years, studies have reported cases of canine ehrlichiosis in various parts of the world (Sosa-Gutierrez et al., 2013; Aziz et al., 2022). In our study, the infected dogs resided in urban and rural areas in the semi-arid region (Caatinga biome) of the state of Sergipe, Brazil, which is part of a region considered endemic for vector-borne blood parasitic diseases such as ehrlichiosis, babesiosis, anaplasmosis, leishmaniasis, and other pathogens (Lima et al., 2010; Guedes et al., 2015; Oliveira et al., 2021; Silva et al., 2024). However, it is important to note that studies have already reported the spread of ehrlichiosis to new geographical areas (Diniz and Moura de Aguiar, 2022). This phenomenon may be related to globalization, urbanization, global warming, and the increase in trade and travel (Sainz et al., 2015).

In the epidemiological chain of transmission of rickettsial pathogens, an important aspect is related to the knowledge of vectors, particularly in identifying the species of ticks and fleas involved in the biological cycle (Philippon, 2006; Huntington et al., 2017). In the canine patients that succumbed to complications from ehrlichiosis, both ticks and fleas were identified, with a notable infestation by the brown dog tick (Rhipicephalus sanguineus). This tick is considered one of the most widespread in the world and is responsible for transmitting not only Ehrlichia canis but also other pathogens such as Anaplasma platys, Babesia vogeli, Bartonella sp., and Hepatozoon canis (Chao and Shih, 2016; Giannelli et al., 2017; Snellgrove et al., 2020; Wechtaisong et al., 2020).

Fleas belonging to the species Ctenocephalides felis felis were identified parasitizing only the canine patient that resided in the rural area. Despite the absence of felines on the property, their transmission to dogs could be linked to the presence of stray animals (Paz et al., 2015), livestock (e.g., Nelore cattle) (Paz et al., 2022), and wild mammals (Lignon et al., 2023). Although fleas are not considered vectors of Ehrlichia canis in pets, these insects can transmit various pathogens (e.g., Rickettsia, Bartonella), some of which are important for public health (Nziza et al., 2019; Nguyen et al., 2020). In addition to this, they can cause clinical issues such as discomfort, irritation, allergic reactions, and anemia (Traversa, 2013).

In both canine patients in this study, severe clinical manifestations were observed, which likely contributed to the animals' deaths. However, in some cases, ehrlichiosis can be considered subclinical, characterized by the absence of clinical or laboratory abnormalities (Komnenou et al., 2007; Mittal et al., 2017). Nonetheless, the emergence of clinical signs is often inevitable, as silent changes tend to progress, such as glomerular and tubular alterations that significantly contribute to renal failure in animals (Crivellenti et al., 2021). For these reasons, canine monocytic ehrlichiosis is considered a multisystemic disease (Foglia et al., 2006), and it is important to note that coinfection with two or more hemoparasites in a patient can occur (Sambri et al., 2004; Mylonakis et al., 2005). In such cases, it is difficult to attribute the clinical signs, hematological, and biochemical changes to a single parasite (Foglia et al., 2006).

For the diagnosis of ehrlichiosis, parasitological, serological, and molecular tests can be used (Waner et al., 2001; Santamaria et al., 2014). In the canine patients reported in our study, diagnosis was achieved through the visualization of morulae of the parasite in neutrophils and monocytes, combined with serological testing. These are considered valuable traditional diagnostic techniques for monocytic ehrlichiosis (Harrus and Waner, 2011). In addition to these, complementary tests should be requested, not only to aid in the diagnosis of the infection but also to assess the vital functions of various organs, hematological parameters, and serum levels of hepatic and renal enzymes (Angkanaporn et al., 2022).

The treatment of dogs with monocytic ehrlichiosis using doxycycline can help restore blood parameters such as platelets and eosinophils, but it may also increase levels of interleukins and monocytes (Cardoso et al., 2023). Additionally, studies indicate that doxycycline is a highly effective medication for treating E. canis infections due to its ability to penetrate cells (Mylonakis et al., 2019). In our patients, along with the tetracycline-class antimicrobial, adjunctive medications were added to achieve a better therapeutic response (Mello and Sanches, 2023).

Another important point related to the therapy of dogs with monocytic ehrlichiosis (CME) is that the complete eradication of Ehrlichia sp. can be challenging, and the prognosis is considered severe when patients are in the chronic phase of the disease (Harrus et al., 1997; Sainz et al., 2015). This may account for the deaths of the canine patients reported in our study.

CONCLUSION

Therefore, it can be concluded that EMC is a serious, complex parasitic disease with various clinical manifestations, and despite the use of different medications, the involvement of vital organs can complicate treatment and lead to the death of the animals.

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FUNDING

I am grateful for the support and funding/scholarship from the Coordination for the Improvement of Higher Education Personnel - CAPES.

DATA AVAILABILITY STATEMENT

The research data are not available.

*Corresponding author:

[e-mail]

Editor-chefe:

Marcelo Resende de Souza

Editor-científico:

Antônio de Pinho Marques Jr.

Publication Dates

• Publication in this collection
  10 Aug 2026
• Date of issue
  2026

History

• Received
  09 Jan 2026
• Accepted
  17 Mar 2026