Concurrent generalized demodicosis and leishmania infections in a dog

This article describes a rare case of concurrent infections of a dog with leishmaniasis and demodicosis. Canine leishmaniosis (CL) with a chronic disease characteristic, possesses multiple systemic signs associated with proliferation of the parasite within macrophages of the mononuclear phagocytic system. The course of infection may be different from one individual dog to another, ranging from spontaneous cure to acute evolution that leads to death, if proper management and therapy are not adopted. A parasitological cure is rarely achieved and clinical recurrences in CL are frequent.

Canine demodicosis is a moderate to severe, noncontagious parasitic skin disease caused by an overpopulation of the host-specific commensal follicular mites. The causative agent (Demodex canis) remains one of the main challenges in veterinary dermatology in many countries. This disease has with two clinical forms namely localized and generalized.

Demodex spp., as normal residents of the fauna, are believed to be host-adapted mites of mammals. The mites have not been shown to cross-infest between dogs and cats, nor are they transmitted to people. However, transmission of mites may also occur during direct contact between older animals. The characteristic of generalized demodicosis (GD) is not well understood, but an abnormal cellular immune response is considered a major pathogenic factor. Generalized demodicosis usually means that the dog has a serious underlying disease that is weakening the immune system, thereby making the dog susceptible. Demodex  mites may affect the cholinergic pathways to induce immunosuppression in their host and then proliferate incessantly in skin microenvironment to cause demodicosis. A combination of hereditary and immunosuppressive factors such as endocrine disorders, oestrus, whelping, corticotherapy and chemotherapy, suggest that plays a pathogenetic role in the association between demodicosis and immunosuppressive factors. However, certain breeds may have strong predisposition. Demodicosis therapy is time-consuming and frustrating for both dog owners and veterinarians. Multiple conventional and newer therapeutic options currently exist for generalized demodicosis. Conventional treatment options include Amitraz (Mitaban) and  Macrocyclic Lactone (Ivermectin, Milbemycin oxime and Doramectin and etc). 

Case study:

A 4-year-old male rottweiler dog with a three-month history of generalized erythema, alopecia and severe crusting, was presented to the clinic. The disease had started as an area of alopecia and hyperpigmentation of the left rear limb. Lesions progressively had affected the ventral aspects of the trunk and neck, all four limbs, and most of the head, including both pinnae. Deep pyoderma and furunculosis were the prominent features in this case, causing a severe pruritic dermatitis, with erythema, seborrhoea, hyperpigmentation and haemorrhagic crusts. A generalized lymphadenopathy was noticeable. According to the owner’s statement, weekly rinse with Amitraz and Ivermectin injection had made a slight improvement in the condition, but negative skin scrapings were never achieved. Therefore, the owner elected for euthanasia due to the severity of the coetaneous lesions and poor response to treatment.

In the clinic, multiple positive skin scrapings and cytology confirmed the diagnosis of GD and staphyloccocal folliculitis. The only systemic signs observed were weight loss and mild generalized lymphadenopathy. CL was suspected. As a result, a canine leishmaniasis rapid diagnostic test was performed, using blood serum. Positive serodiagnosis of leishmaniasis changed the entire scenario. Currently, we were dealing with two chronic diseases. On the blood test (CBC), the leukogram pattern revealed regenerative normocytic normochromic anemia (low RBC, Normal MCV, MCH and MCHC, high RDW - %15), leukocytosis and neutrophillia, present. 

The treatment strategy was based on the remission of the parasites as well as reducing the CL antibody titter in order to alleviate the clinical manifestations of the infections. Considering the diagnosis of pancreatitis on ultrasound examination, and since Meglumine antimoniate (Glucantime?), as the drug of choice for treatment of visceral leishmaniasis, may cause pancreatitis, the therapeutic treatment was initiated with daily injection of Marbofloxacin (Marbox?), at the dosage of 2 mg/kg IM, weekly subcutaneous injection of Ivermectin (400 mcg/kg), as well as daily intake of Alluporinol 300mg (10 mg/kg, PO, OID). The clinical improvement was gradually evident over three weeks into treatment. The nutrition was also improved by feeding a balanced, age-appropriate diet. Marbofloxacin injection was stopped on day 20. 

Premature treatment cessation by the owner is usually the central reason for treatment failure and relapsing the condition. Since the clinical signs often improve before the parasitological cure, regularly scheduled follow-up visit to ensure a successful outcome, is required. In our case, after almost two months, the skin lesions were back again, and pyoderma manifested. Macroscopic examination of skin scraps revealed large number of adult demodex mites as well as their eggs.

Therefore, an isoxazoline (Fluralaner {Bravecto, MSD}) as a newly available, flavored, chewable tablet, which is, in fact, labeled for the prevention and treatment of flea and tick infestations in dogs, was prescribed. 

Impression smear from the lesions revealed presence of clusters of gram positive cocci. Culture and sensitivity test revealed the presence of gram positive cocci sensitive to Co-amoxiclav, Amoxicillin, Cephalexine and Ceftriaxone. The secondary bacterial infection (pyodemodicosis) was empirically treated with Co-amoxiclav (20 mg/kg, PO, BID) and other supportive therapy (Zinc + Biotin). Adjunctive topical therapy with an antibacterial shampoo, such as benzoyl peroxide, helped to hasten the clinical resolution. Simultaneously, treatment with Meglumine antimoniate (100 mg/kg Ss, OID) was initiated and carried out for 4 weeks. 

Significant clinical improvement with a remarkable reduction in mite numbers in skin samples was seen by day 42. Two months later, on further examination, no mites were recovered on skin scrapings. Erythema, papules, alopecia, oily seborrhea, edema, hyperpigmentation, and crusts were gradually disappeared. 

Yet, the dog is on constant monitoring, to make sure that the dog stays in good condition.