Arthropod-Vector Borne Infectious Diseases in Small Animals Flashcards
What are vector-borne diseases caused by?
Parasites, bacteria or viruses transmitted by the bite of haematogenous arthropods
What is the purpose of the Pet Travel Scheme (PETS)?
To protect individual pets but also UK disease status and requires rabies and tapeworm treatment
What changes have recently been made to the PETS?
On 1st Jan 2012 the requirement for compulsory treatment of companion animals for ticks before their entry into the UK was withdrawn
What tick borne diseases may be imported in dogs travelling in from the EU?
Babesia canis canis
Babesia gibsoni
Ehrlichia canis
What tick borne diseases are already endemic in the UK?
Borrelia burgdorferi
Anaplasma phagocytophilum
Which ticks are already endemic in the UK?
Ixodes ricinus
Dermacentor reticulatus
Which tick is brought into the UK on animals?
Rhipicephalus sanguineus - not endemic in UK and requires >18C for life cycle, vector for Mediterranean spotted fever
What is babesiosis caused by?
Protozoan parasite of RBCs transmitted by ticks
2 main genera are Babesia and Theileria = Piroplasms
What are the most important agents of canine babesiosis?
Large babesia = B. canis canis (Europe), B. canis vogeli (Africa, Asia, USA, Europe, Australia), B. canis rossi (S. Africa)
Small babesia = B. gibsoni (Asia, Africa, USA, S. Europe)
What differences exist between the different species of babesia?
Vectors and geographical distribution (changing)
Virulence, prognosis and response to treatment
What is the pathogenesis of babesia?
Within ticks Babesia is transmitted trans-stadially and trans-ovarially
Sporozoites injected from tick salivary glands, enter circulation and endocytosed by RBCs
Immune-mediated component of pathology
Thrombocytopaenia common but usually not enough to cause bleeding or abnormal coagulation
What are the clinical signs of babesiosis?
Those of haemolytic anaemia
Lethargy, depression, inappetence, icterus, splenomegaly, tachycardia, tachypnoea
How is babesia diagnosed?
Clinical lab findings - thrombocytopaenia, Coombs +ve
Microscopic identification - low sensitivity
PCR - high sensitivity, species identification possible
Serology - indirect fluorescence Ab test/ELISA
What is the treatment for babesiosis?
Antibabesial drug - Imidocarb dipropionate
Large forms = rapid clinical response
Small forms = clinical and pathological cure uncommon, clinical relapses can occur
Which rickettsial diseases are vector borne?
Canine Ehrlichia and Anaplasma spp
Small obligate intracellular gram -ve bacteria
Which species infect monocytic cells?
Ehrlichia canis
Ehrlichia chaffeensis which causes human form but molecular evidence has been found in canine form
Which species infects thrombocytic cells?
Anaplasma platys
Which species infects granulocytic cells?
Anaplasma phagocytophilum
Ehrilichia erwingii
What is the incubation period of Ehrlichia canis?
1-3 weeks
What are the acute signs of Ehrlichia canis?
Vasculitis and immune destruction causing thrombocytopenia and coagulopathy
Multisystemic signs
Spleen and LN enlargement
CNS/ocular sings
What are the two outcomes of acute Ehrlichia canis?
Clearing of disease
Sub-clinical carriers
What can happen to the sub-clinical carriers of Ehrlichia canis?
Recover or become chronically infected
What are the signs of chronic Ehrlichia canis infection?
Bone marrow destruction causing a pancytopenia
Signs as for acute
How is Ehrlichia canis diagnosed?
Morulae in monocytes in blood smears or macrophages from tissue aspirates
Thrombocytopaenia/pancytopaenia
IFA/ELISA
How is Ehrlichia canis treated?
Tetracyclines/Chloramphenicol for 28 days
What are the signs of A. phagocytophilum in dogs?
Mild/moderate thrombocytopaenia
Lymphopaenia
Mild anaemia
Natural chronic infection hasn’t been seen
Impaired PMN function can predispose to secondary infections
What are the clinical signs of Lyme disease in people?
Erythema migrans in 80-90% of cases
Later clinical signs involve skin, nervous/musculoskeletal systems
What are the commonest signs of Lyme disease in dogs?
Lethargy, anorexia and pyrexia
Inflammatory polyarthritis
Lymphadenopathy
Protein-losing glomerulonephropathy
How is diagnosis of Lyme disease achieved in dogs?
No pathognomonic test
Asymptomatic seroconversion common
Microscopic/genetic detection often not possible
What is the treatment for Lyme disease in dogs?
Doxycycline/amoxicillin
What are the characteristics of Leishmania?
Flagellate protozoa
Phlebotomus vector - sandflies
Reservoir host - dogs
What is the life-cycle of Leishmania?
IMAGE
What are the key features of pathogenesis of canine leishmaniosis?
Macrophages are target tissues
Systemic infection in haemolymphatic organs
Parasite persistence can lead to chronic infection
Protective immunity mediated by T cells
Signs may develop months-years after infection
How does host immune response determine clinical outcome?
Th2 predominant = severe non self-limiting disease with high serology, decreased cellular immunity and high parasite load
Th1 predominant = clinically healthy but infected self-limiting disease with low serology, predominant cellular immunity, low parasite load
What other factors influence variation of clinical outcome?
Endemic/naive situation,
2-4 years and >7 years more susceptible
Breed, nutrition, concurrent disease and immunosuppression
What are the clinical signs of leishmaniosis?
Weight loss, lethargy, inappetence, skin disease, lymphadenomegaly, splenomegaly, lameness, arthropathy, PU/PD, proteinuria, ocular signs, epistaxis, GI signs, hypergammaglobulinaemia, non-regenerative anaemia or mild thrombocytopaenia, azotaemia
How is leishmaniosis diagnosed?
Demonstration of parasite (100% spec, 80% sens)
Serology with high Ab titre highly suggestive
PCR of bone marrow/LN/spleen/skin
Clinicopathological findings - hyperglobulinaemia, decreased albumin:globulin ratio, thrombocytopaenia, non-regenerative anaemia, proteinuria
What is the treatment for leishmaniosis?
Meglumine antimoniate + allopurinol (prolonged treatment) and needs importation as not licensed in UK
What does Diroflaria immitis cause?
Heartworm
Occupy R side heart and pulmonary arteries
What are the clinical signs of D. immitis?
Coughing, dyspnoea, reduced exercise tolerance, R sided heart failure
What vector transmits D. immitis?
Mosquito
What are the prophylactic treatments for D. immitis?
Selamectin (Stronghold)
Milbemycin (Program Plus/Milbemax)
Moxidectin (Advocate)
What is the treatment for D. immitis infection?
Symptomatic treatment with steroids and treatment of CHF
Adulticide therapy using melarsomine
Microfilarial therapy using levamisole, ivermectin, milbemycin
What is Bartonellosis?
Caused by small gram -ve haemotropic bacteria
Which species of Bartonella is most common in cats?
Bartonella henselae most common in cats
What is the vector for Bartonella?
Fleas
Ticks?
How are zoonotic bartonella infections caused?
Cat scratch disease
