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Leishmaniosis in other animals

Even though the dog is the main reservoir of Leishmaniosis, there are other animals such as hares and rabbits, goats, rodents, cats, and even birds that can be effective reservoirs, and may therefore be involved in the transmission of Leishmania. It is very important to control the pathogen in these animal populations in order to prevent their role as active reservoirs. These animal species do not directly spread the parasite, but the Infection is always conducted through the vector. Therefore, it is important to prevent sandflies bites by avoiding to transit outside during dusk or at dawn, or by wearing appropriate protective clothing and using repellents.

Leishmaniosis in cats

Infection by Leishmania in cats is not uncommon and has been described in virtually all areas where canine Leishmaniosis is endemic, although they are considered as a secondary reservoir. However, it seems that only a very small proportion of these animals develop the disease, probably due to the cat's immune system being able to control the infection of this parasite by either eliminating it or by keeping it in a chronic/subclinical state. More than 70% of the published cases were diagnosed in animals with compromised immunity (viral infections, immunosuppressive treatments, neoplasias, etc.). Retroviral infections such as Feline Leukemia and Feline Immunodeficiency creates an immunosuppression of the animal, making such kind of infected cats more vulnerable to other diseases such as Leishmaniosis. Whenever there is a FIV or FeLV infection, if the cat becomes infected with Leishmania the immune response of the cat to the parasite is severely reduced, leading to false negatives when serological techniques are used.

In the Autonomous Community of Madrid, prevalence in cats sampled in the surroundings of the outbreak varies from 3.2% to 9.3% .

Symptoms of leishmaniosis in cats

Regarding the clinical presentation, the cutaneous symptoms predominate in 65% of the cases (dermatologic abnormalities include nodules, ulcerations and less often exfoliative dermatitis), similar to those observed in canine leishmaniosis. Other common symptoms in feline leishmaniosis include mucocutaneous lesions and lymph node enlargement, mainly in the head and neck, or the hands and feet. The systemic symptoms are nonspecific and among them we can find lymphadenomegaly, splenomegaly, anorexia, weight loss, etc.

Diagnosis of leishmaniosis in cats

Most diagnostic techniques for Leishmania infection which are available for dogs can be used in cats. Diagnosis is made in most cases by immunological, cytological, histological, culture or molecular methods.

  • Cytological examination of samples from enlarged cutaneous lesions, mucous membranes and lymph nodes.
  • Blood and bone marrow smears.
  • Cutaneous biopsy for conventional staining (H & E) and immunohistochemistry.
  • Quantification of anti-Leishmania antibodies with serological techniques adapted to the cat. In the case of high suspicion and low antibody titers or even in the case of negative results, it is advisable to perform molecular techniques to rule out the disease.

In addition, it is highly probable that the cat might have an underlying or concurrent disease, so basic laboratory tests, including blod count, biochemistry, urinalysis and serum proteinogram should be performed.

Treatment and prevention of leishmaniosis in cats

Similarly to what is done in the dog, the treatment in cats consists in overcoming the parasite and the symptoms, although the main issue is to prevent the disease and to keep the immune system as active as possible to avoid an infection or a relapse. In order to achieve this, it is crucial to ensure that the cat does not suffer from other pathologies.

Due to the absence of studies on vaccines against Leishmania in cats, the best strategy to prevent Leishmania infection in this species would be to use topical insecticides, applying chemical compounds with sand fly repellent activity, similar to those used for dogs. The use of this kind of preventive methods against sand flies are the key factor to avoid leishmaniosis, especially in the case of cats living in areas of high risk, such as the Mediterranean basin. Pipette, necklace and aerosols are formats available in cats to protect them from the vector. However, the choice of the product should be supervised by the veterinarian in order to ensure both the efficacy of the product and the health of the animal (i.e. most pyrethroids, like permethrin and deltamethrin, cannot be used in cats due to their toxicity to this species).

Leishmaniosis in hares and rabbits

Although it has been described that other animals, in addition to the dog, may be infected with Leishmania, its epidemiological role is generally very limited. However, in recent years it has been shown that under certain circumstances secondary reservoirs may play an important role in human leishmaniosis outbreaks. This has been the case of the outbreak of the Autonomous Community of Madrid in which a new cycle of sylvatic transmission has been described and in which the leporids have acted as the main reservoir and source of the disease for humans. This was demonstrated trough xenodiagnosis, serology and molecular characterization.

Human Leishmaniosis outbreak in the southwest area of the Autonomous Community of Madrid

In 2009, the alarms went off when an increase in the number of human leishmaniosis cases was noticed in the southwest area of the Autonomous Community of Madrid, including four nearby municipalities (Fuenlabrada, Leganés, Getafe and Humanes de Madrid), and which finally was the largest outbreak of human Leishmaniosis declared in Europe. It remains active, having affected, since July 2009 to date, more than 690 people (38% affected by visceral Leishmaniosis and 62% by cutaneous Leishmaniosis).

This rise of human cases was not correlated to an increase of canine Leishmaniosis and this fact suggested that it could be due to the emergence of new key reservoirs: the hare and the rabbit. Regarding these reservoirs, it was already known that both species, hares and rabbits, are capable of transmitting Leishmania to the sandfly, as demonstrated by the xenodiagnostic studies performed in both species. This increase in the density of hares in the area of the outbreak (mainly caused by urban changes in previous years and the absence of natural predators) and the anti-Leishmania seroprevalence found in them (74.1% positive and 31.8% with titers greater than 1 / 400 according to Moreno et al., (2013) suggested that hare was the most important reservoir in the outbreak. The rabbit, also implicated, would contribute in a lesser extent to maintain the infection. In addition, the presence of Leishmania DNA in spleen and skin samples in both species taken in different areas of Madrid and Spain, demonstrated the widespread presence of Leishmania in rabbits and hares, suggesting that under certain epidemiological circumstances, new similar outbreaks may occur.

The species responsible for the outbreak was shown to be L. infantum, specifically the ITS-LOMBARDI genotype. It was noticed that 70% of the human cases corresponded to immunocompetent people, between 40 and 60 years of age, leading to the suspicion that a more virulent strain of L. infantum was circulating in the region. Analysis of the ex vivo virulence of two isolates (BOS1FL1 and POL2FL7) from the outbreak area showed that virulence was significantly greater than the characteristic virulence of the strain commonly isolated in Madrid since 1992.

Regarding the vector, the main species in the area of the outbreak and the only one of which Leishmania has been isolated was P. perniciosus, although the presence of Sergentomyia diminuta and P. ariasi was also proved. The density of P. perniciosus was considerably increased during the outbreak, reaching 143 sandflies/m2 in the year 2012 (before the outbreak the average was 30 sandflies/m2). The prevalence of L. infantum in P. perniciosus collected in the outbreak area was 58.5% according to Jimenez et al. (2013), which shows the high rate of transmission of Leishmania existing at that time. The vector also showed preferences for feeding. When blood was collected from the interior of the sandflies, 60% came from hares, 30% from humans and 10% from cats.

In hares and rabbits, Leishmaniosis courses asymptomatically without causing disease, as it occurs in most wild reservoirs.

Due to the coordinated efforts of several health professionals and the regional administration in order to stop the increase in human cases and to advance in the knowledge of the vector, reservoirs, the parasite itself and the relationship between them, a downward trend in the number of cases from 2012 to the present has been achieved.

In addition to the scientific advances mentioned above, a series of actions have been carried out to control the progression of the infection. A plan to control both the reservoir and the vector was implemented, in addition to the enforcement of environmental measures, managed by the Regional Administration in collaboration with the involved City Councils and with the support of various research centers (Carlos III Health Institute, VISAVET, Faculty of Veterinary Medicine of the Complutense University and Faculty of Biological Sciences of the Complutense University, among others).

The actions carried out were:

  • Reservoirs: control of hare and rabbit populations in the affected area, in addition to the closure of the warrens. Parasite surveillance was increased and serological (IFI) and molecular techniques (PCR) were used to detect the circulation of Leishmania in these animal populations. In addition, different research lines were promoted.
  • Vector: a monitoring program at risk points was carried out through the collection of specimens with adhesive and light traps. A debug program was also established.
  • Environmental control: sanitation measures have been implemented at risk points (clearing, sewer cleaning, rubbish and debris elimination, sludge removal, etc.). The collection of abandoned animals was also enforced.
  • Communication and education: in addition to strengthening the surveillance, the communication of the outbreak situation to health professionals was promoted and recommendations were sent to individuals. Several technical documents, posters, brochures, online information, etc. have been produced and scientific sessions have been held.