Infectious diseases of pet animals can be categorized according to their causative agents: viruses, bacteria, fungi and parasites, or they can be divided according to the body systems which they affect, or according to their paths of transmission. In that respect, the diseases transmitted by arthropod vectors, (e.g., vector-borne diseases) are of special interest, and frequently comprise a diagnostic challenge. Recently, some new non-invasive diagnostic techniques have been developed to detect pet vector-borne diseases.
Companion animal or pet vector-borne diseases include a number of infections which are transmitted by hematophagous arthropod vectors including ticks, fleas, sand flies and mosquitoes. Some of the most important diseases which belong to this group are leishmaniosis, borreliosis, ehrlichiosis, anaplasmosis, babesiosis, bartonellosis, dirofilariasis and hepatozoonosis. The distributions of these diseases are often related to the distributions of their vectors; however, some infections may be found also in "non-endemic" areas due to dog travel, or the existence of alternative modes of transmission in addition to the transmission by arthropods, for instance transplacental or venereal transmission, direct animal to animal transmission, or transmission by blood product transfusion.
The most common diagnostic techniques for vector-borne diseases include detection in blood smears or tissue cytological preparations by light microscopy; detection of specific antibodies by various serological methods; or molecular detection of specific DNA from the suspected pathogens by the polymerase chain reaction (PCR) or a related technique. Most of these diagnostic techniques rely on testing samples that were collected by conventional sampling methods such as venous blood collection and aspirations of lymph nodes or the bone marrow.
"Non-invasive" diagnostic techniques consist of sampling techniques that do not require penetration of the skin or a mucosal barrier in order to obtain the sample material. In that respect, venipuncture to obtain blood; aspiration of the bone marrow, lymph node or spleen, and skin biopsies or scraping, are invasive sampling techniques. Conjunctival and oral mucosal swabs, saliva analysis, PCR on hair, and urine tests using free-catch urine, are non-invasive techniques.
Non-invasive conjunctival PCR has been shown to be accurate in the diagnosis of seropositive dogs with clinical leishmaniosis1,2 and ehrlichiosis3, and also useful in the detection of asymptomatic Leishmania infantum infection4,5. Oral swab PCR has been shown to be considerably less sensitive than conjunctival PCR for leishmaniosis.6 Recently PCR of hair has been shown to be sensitive for detection of infection in dogs with clinical leishmaniosis7, and urine PCR may also be useful in the detection of Leishmania infection8,9.
It appears that non-invasive conjunctival PCR is a good molecular tool for the detection of L. infantum infection in epidemiological surveys, clinical studies, and in clinical situations when invasive detection of infection is not desirable. Additional non-invasive sampling methods are useful for the diagnosis of other vector-borne diseases and also for infections transmitted by other means.
References
1. Strauss-Ayali D, Jaffe CL, Burshtain O, Gonen L, Baneth G. Polymerase chain reaction using noninvasively obtained samples, for the detection of Leishmania infantum DNA in dogs. J Infect Dis. 2004;189:1729–1733.
2. Ferreira Sde A, Ituassu LT, de Melo MN, de Andrade AS. Evaluation of the conjunctival swab for canine visceral leishmaniasis diagnosis by PCR-hybridization in Minas Gerais State, Brazil. Vet Parasitol. 2008;152:257–263.
3. Baneth G, Harrus S, Ohnona FS, Schlesinger Y. Longitudinal quantification of Ehrlichia canis in experimental infection with comparison to natural infection. Vet Microbiol. 2009;136:321–325.
4. Leite RS, Ferreira Sde A, Ituassu LT, de Melo MN, de Andrade AS. PCR diagnosis of visceral leishmaniasis in asymptomatic dogs using conjunctival swab samples. Vet Parasitol. 2010;170:201–206.
5. Di Muccio T, Veronesi F, Antognoni MT, Onofri A, Piergili Fioretti D, Gramiccia M. Diagnostic value of conjunctival swab sampling associated with nested PCR for different categories of dogs naturally exposed to Leishmania infantum infection. J Clin Microbiol. 2012;50:2651–2659.
6. Lombardo G, Pennisi MG, Lupo T, Migliazzo A, Caprì A, Solano-Gallego L. Detection of Leishmania infantum DNA by real-time PCR in canine oral and conjunctival swabs and comparison with other diagnostic techniques. Vet Parasitol. 2012;184:10–17.
7. Belinchón-Lorenzo S, Iniesta V, Parejo JC, Fernández-Cotrina J, Muñoz-Madrid R, Soto M, Alonso C, Gómez Nieto LC. Detection of Leishmania infantum kinetoplast minicircle DNA by Real Time PCR in hair of dogs with leishmaniosis. Vet Parasitol. 2013;192:43–50.
8. Solano-Gallego L, Rodriguez-Cortes A, Trotta M, Zampieron C, Razia L, Furlanello T, Caldin M, Roura X, Alberola J. Detection of Leishmania infantum DNA by fret-based real-time PCR in urine from dogs with natural clinical leishmaniosis. Vet Parasitol. 2007;147:315–319.