Case ReportReemergence of Dourine in Italy: Clinical Cases in Some Positive Horses
Introduction
Dourine is a parasitic venereal disease of equines caused by a flagellate protozoan of the species Trypanosoma equiperdum. It is the only trypanosomiasis that is not transmitted by blood-feeding vectors. Dourine can affect horses, mules and donkeys. The latter are generally more resistant and often remain asymptomatic carriers. The infection is endemic in many areas of Asia, Africa, Russia, Middle East and Eastern Europe (World Organisation for Animal Health [OIE] data). Its course and clinical signs vary considerably depending on the virulence of the strain concerned, as described in the literature on this topic. The course of the disease in horses is chronic, varying from a few months to 1-2 years. A number of authors have broken the course down into three stages: stage 1 (genital lesions), stage 2 (cutaneous signs) and stage 3 (nervous signs) [1], [2]. Stage 1 involves genital edema and swelling, manifesting 1-2 weeks after infection. In stage 2, typical cutaneous plaques (“silver dollar” plaques) appear, with thickening of the skin, considered pathognomonic by some authors [1], [3], [4]. Stage 3 is characterized by progressive anemia, neurological disorders and paresis of the hindquarters, often ending in death. Mortality rate is high, at around 50% [3].
Before the recent epidemic, the last case notified in Italy was in 1998, when an asymptomatic stallion in the province of Padova tested positive with a titer of 1:6 on complement fixation (CF) testing. The last reported cases of Dourine-positive horses with clinical signs date back to the epidemic of the 1970s [5]. On May 19, 2011, a stallion undergoing routine serological testing in the province of Catania for stud purposes tested positive on CF. The epidemiological investigation that followed resulted in the identification of other holdings epidemiologically linked with the infected animals in southern Italy. The Italian Ministry of Health emanated an ad hoc surveillance plan with mandatory testing of all equines of reproductive age in Italy. This plan has so far led to the identification of seven outbreaks involving 20 positive animals.
Five positive animals previously destined for slaughter were transferred to the Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise “G. Caporale” (Istituto G. Caporale) for inclusion in a study to investigate the pathogenesis and attempt the isolation of T. equiperdum, which is very difficult, as demonstrated by the low number of isolates in the past decades [3], [6].
The long period of the disease’s absence—from the epidemic in the 1970s to that of 2011—has resulted in a knowledge gap in generations of veterinarians. The literature on this topic is generally old and lacking in graphic evidence, as this disease is not generally present in developed countries. Moreover, Dourine is a chronic disease whose signs are not constantly present and whose pathogenicity can vary, depending on the strain concerned. Therefore, the aim of this study was to describe and provide graphic evidence of the signs observed during the recent outbreaks of Dourine.
Section snippets
Animals
Eight horses were observed (Table 1, Table 2, Table 3). One was studied at the holding concerned, whereas five naturally infected and two experimentally infected horses were observed at the Istituto G. Caporale. Experimental infection was carried out by blood transfusion from infected horses with clear signs of Dourine.
The age range of the horses in the study was 4-16 years. Most of them were half-breeds used for meat production. There were six mares and two stallions. The seven animals studied
Results
In Table 4, a value (0 or 1) is attributed to a given sign in each horse on the basis of its presence or absence. In this way, it is possible to establish which signs were most common and which horse presented the most signs at the same time.
Genital Edema
Slight oedema of the sheath was seen in one stallion. In one mare, oedema of the vulva was accompanied by ulcers along the rim of the vulva. The severity of these genital oedemas varied considerably. They were not observed in the animals infected experimentally (Fig. 2).
Edematous Cutaneous Wheals and Plaques
Wheals or plaques were found on the skin of both naturally and experimentally infected animals. The wheals varied in shape (roundish, oval or irregular) and size (from a few millimeters to a few centimeters) and were found on the trunk, neck, chest and shoulders. Numerous wheals appeared contemporaneously, developing quickly and suddenly. They were seen for a few hours to a few days and then disappeared, often reappearing in a different area. A “silver dollar” plaque was seen in just one
Nervous Signs
Three animals (Table 4) presented stiffness, weakness, lameness in one or more hind legs, staggering, lack of coordination, inability to stand upright after prolonged sternal or lateral recumbency and ataxia. When standing, animals often stood with the legs well splayed, especially the hind legs. The left hind leg of one animal often dragged on the ground, causing deformation of the hoof wall. As the disease progressed, the difficulties in movement became ever more evident and the affected
Increased Synovial Fluid
Increased synovial fluid and consequent joint ectasia were found in 50% of the symptomatic horses (Table 4). The joints affected were as follows: pastern, hock and carpus, with synovial fluid testing positive on PCR. In one animal the parasite could be seen on microscopic examination of synovial fluid from the hock joint.
Fever
No animal presented significant fever during the observation period.
Eye Lesions: Conjunctivitis and Keratitis
Mild corneal opacity was observed in just one experimentally infected animal. PCR of the conjunctival swab
Discussion
Data collected in this study demonstrate that most of the signs observed coincide with those reported in the few available literature studies. The stages of the disease described in the past and related to pathogenesis also occur in the same order today. The horses observed can be divided into three main groups: naturally infected mares (group 1), naturally infected stallions (group 2), and experimentally infected mares (group 3).
No rise in body temperature was observed in any of the infected
Conclusion
Given the extreme variability of signs in infected animals, difficulties in clinical diagnosis, and the lack of Europe-wide active surveillance plans, it is important to observe and report new cases of Dourine. Difficulties regarding the isolation of the T. equiperdum should stimulate more interest in the experts’ community.
References (16)
- et al.
Trypanosoma equiperdum, historical mistake or master in disguise?
Trends Parasitol
(2005) - et al.
Trypanosoma evansi and T. equiperdum: distribution, biology, treatment and phylogenetic relationship (a review)
Vet Parasitol
(1998) - et al.
Efficacy of cymelarsan and diminasan against Trypanosoma equiperdum infections in mice and horses
Vet Parasitol
(2010) - et al.
Real-time PCR for detection of Trypanosoma brucei in human blood samples
Diagn Microbiol Infect Dis
(2004) Il Morbo coitale maligno
Clin Vet (Milano)
(1946)Manual of diagnostic tests and vaccines for terrestrial animals
- Bellani L, Papalia S, Caporale EP. Report on dourine epidemiological surveillance and research in Italy. In: Report of...
- et al.
Body condition scoring and weight estimation of horses
Equine Vet J
(1988)
Cited by (21)
Treatment Efficiency of Combination Therapy With Diminazene Aceturate and Quinapyramine Sulfate in a Horse With Dourine
2020, Journal of Equine Veterinary ScienceCitation Excerpt :The clinical signs of dourine include fever, anemia, emaciation, local edema of the genitalia and mammary gland, skin lesion, paralysis, and ataxia [25]. Despite no apparent skin lesion, the clinical picture of the stallion in the present study corresponded well with those of reported cases of dourine (Fig. 1, Table 1) [26]. Recombinant T. evansi GM6-based ELISA and ICT can help detect the anti-T.
Tissue (re)distribution of Trypanosoma equiperdum in venereal infected and blood transfused horses
2019, Veterinary ParasitologyCitation Excerpt :The presence of neurological signs confirms the tropism of T. equiperdum for the peripheral nervous system and the lack of involvement of the central nervous system, in contrast with other trypanosomes. Corneal opacity was found in two stallions and one mare and was consistent with previous reports (Alemu et al., 1997; Vulpiani et al., 2013). Aqueous intraocular fluid collected at necropsy from the eye suffering this corneal opacity was also positive for the parasite DNA in the RT-PCR.
Infectivity and virulence of Trypanosoma evansi and Trypanosoma equiperdum Venezuelan strains from three different host species
2018, Veterinary Parasitology: Regional Studies and ReportsIgG antibodies from dourine infected horses identify a distinctive Trypanosoma equiperdum antigenic pattern of low molecular weight molecules
2013, Veterinary Immunology and ImmunopathologyCitation Excerpt :After sporadic reports at the end of the 1990s (OIE, 2011), there was a new outbreak in May 2011 (Scacchia et al., 2011). Clinical findings, laboratory and epidemiological investigations suggested that all recent Italian outbreaks were caused by T. equiperdum and were related to sexual transmission (Scacchia et al., 2011; Calistri et al., 2012; Podaliri Vulpiani et al., 2012). The parasite was never detected by microscopy in the blood stream of infected animals over a period of weeks or months.
Diagnosis of dourine in outbreaks in Italy
2013, Veterinary Parasitology