**4. Treatment of animals infected with leishmaniasis using PDT**

PDT has emerged in the treatment of cutaneous diseases among human and different animal species [41]. Researchers have shown that PDT offers an effective alternative in the treatment of CL indicating that it also has a great clinical potential in the treatment of this disease within Veterinary Medicine [27]. The initial studies using PDT to treat leishmaniasis were performed in humans and are further described on section 7 [31-35]. Although some animals, especially mammals, constitute important reservoirs of the parasites, leishmaniasis also has clinical importance because some species can develop injuries, become sick and die due to the disease and its complications. Therefore, from this point of view, Veterinary Medicine has special interest, not only to control the disease epidemiology, but also to treat infected and sick animals.

The main vertebrate hosts (domestic and wild) described and classified as hosts of these protozoan through natural and/or experimental infections, are: foxes, opossums, armadillos, anteaters, sloths, rodents, cat, dog, goat, sheep, buffaloes, horses and primates [42-47]. While the treatment of infected animals provides possibilities for partial or total removal of cutaneous lesions, it is still not possible to guarantee the elimination of the infectious agents from the carrier animal, remaining the possibility that it remains as a host reservoir. Therefore, there is a great need to further investigate the treatment of domestic and wild animals with leishma‐ niasis, by using PDT.

Among all involved animals, the domestic dog and some rodents are the main sources of human infection in America and in the Middle East, respectively; therefore, being the majors urban reservoir hosts of leishmaniasis [44,48]. The proximity of this animal to humans complicates the disease control. The lack of identification of infected animals becomes a challenge, mainly due to the numerous generic clinical manifestations, and sometimes the absence of pathognomonic lesions in the dogs [49]. The skin disorders are quite common in animals, and include opaque hair coat, alopecia, depigmentation, hyperkeratosis of nasal plan and digital cushions, mucocutaneous ulcers, intradermal nodules, onychogryphosis and excessive flaking [50,51] but the most common presentation of the cutaneous disease is a symmetrical alopecia accompanied by intense flaking with silvery appearance that often starts on the head and spreads to other parts of the body [52]. However, these symptoms are sometimes not correlated with leishmaniasis. Regarding the condition of the dogs as reservoir hosts in the epidemiology of the disease, clinical treatment is not recommended so far [51], making euthanasia of the infected animals mandatory in many countries [50] and keeping the controversial discussion among public health authorities, animal protectors and veterinarians [53,54]. Despite the importance of dogs in the epidemiology of the disease, the most used animal model and the one that has shown success in the treatment of the cutaneous disease are rodents, mainly mice and hamsters.

Several studies demonstrated the possibility of using PDT in animal models, especially on murines. In 2007 *Akilov et al.* reported an evaluation of the use of ALA (precursor of PpIX) in TL caused by Old World species in ears of Balb/c mice [55]. *Akilov et al*. also highlighted the action of ALA-PDT in murine with leishmaniasis compared to a control group treated with ALA [56]. The results showed a significant reduction of 24.5 folds in the parasite load compared with the control group. Nevertheless, they observed vascular damage in ears of the PDT-ALA group probably caused by PDT. According to the authors, a wide inflammatory and immu‐ nologic response was noted in Balb/c ears of ALA-PDT group, which correlated with the expressive decrease of parasite load and with the healing of the tissue.

of PDT to deliver better results compared to traditional treatments, emphasizing its better effectiveness in leading to amastigote-free lesions in a shorter time periods, in addition to its

PDT has emerged in the treatment of cutaneous diseases among human and different animal species [41]. Researchers have shown that PDT offers an effective alternative in the treatment of CL indicating that it also has a great clinical potential in the treatment of this disease within Veterinary Medicine [27]. The initial studies using PDT to treat leishmaniasis were performed in humans and are further described on section 7 [31-35]. Although some animals, especially mammals, constitute important reservoirs of the parasites, leishmaniasis also has clinical importance because some species can develop injuries, become sick and die due to the disease and its complications. Therefore, from this point of view, Veterinary Medicine has special interest, not only to control the disease epidemiology, but also to treat infected and sick

The main vertebrate hosts (domestic and wild) described and classified as hosts of these protozoan through natural and/or experimental infections, are: foxes, opossums, armadillos, anteaters, sloths, rodents, cat, dog, goat, sheep, buffaloes, horses and primates [42-47]. While the treatment of infected animals provides possibilities for partial or total removal of cutaneous lesions, it is still not possible to guarantee the elimination of the infectious agents from the carrier animal, remaining the possibility that it remains as a host reservoir. Therefore, there is a great need to further investigate the treatment of domestic and wild animals with leishma‐

Among all involved animals, the domestic dog and some rodents are the main sources of human infection in America and in the Middle East, respectively; therefore, being the majors urban reservoir hosts of leishmaniasis [44,48]. The proximity of this animal to humans complicates the disease control. The lack of identification of infected animals becomes a challenge, mainly due to the numerous generic clinical manifestations, and sometimes the absence of pathognomonic lesions in the dogs [49]. The skin disorders are quite common in animals, and include opaque hair coat, alopecia, depigmentation, hyperkeratosis of nasal plan and digital cushions, mucocutaneous ulcers, intradermal nodules, onychogryphosis and excessive flaking [50,51] but the most common presentation of the cutaneous disease is a symmetrical alopecia accompanied by intense flaking with silvery appearance that often starts on the head and spreads to other parts of the body [52]. However, these symptoms are sometimes not correlated with leishmaniasis. Regarding the condition of the dogs as reservoir hosts in the epidemiology of the disease, clinical treatment is not recommended so far [51], making euthanasia of the infected animals mandatory in many countries [50] and keeping the controversial discussion among public health authorities, animal protectors and veterinarians [53,54]. Despite the importance of dogs in the epidemiology of the disease, the most used animal model and the one that has shown success in the treatment of the cutaneous disease

**4. Treatment of animals infected with leishmaniasis using PDT**

excellent esthetic results.

398 Leishmaniasis - Trends in Epidemiology, Diagnosis and Treatment

animals.

niasis, by using PDT.

are rodents, mainly mice and hamsters.

Despite ALA, other classes of photosensitizers already widely used in PDT began to be tested. The phenothiazine 3,7-bis(di-n-butylamino)phenothiazin-5-ium bromide (PPA904) was tested by *Akilov et al.* in mice [57]. Ears of female Balb/c were infected with metacyclic parasites of *Leishmania* sp. Following infection, mice were treated with PPA904 cream and irradiated with a broad band light source. They tested the PS concentration, time of uptake and absorption site in the ear. The results showed that PPA904 applied during at least 90 min in consecutive sessions of PDT decreased parasite load around 5.2 log compared to the controls groups. However, PPA904 application also lead to skin irritation. Another study was carried out with female Balb/c infected with *L. major* parasites expressing green fluorescent protein (GFP) to monitor the parasitic load and the efficacy of PDT [58]. PPA904 was applied in the ears of the mice and the parasitic load was compared with control group (only infected). The fluorescence of GFP parasite in the ear of mice after the PPA-PDT decrease significantly, about 80%, compared to control group. The authors emphasized that this result was obtained after more than one PDT session.

*Peloi et al.*chosen a different murine, which is also considered an appropriate model to develop leishmaniasis caused by some New World *Leishmania* spp. Hamsters were used to investigate the effectiveness of PDT with methylene blue (MB) photosensitizer [59]. A light-emitting diode (LED) was chosen as light source. The footpads of hamsters were infected with *Leishmania* sp. The control presented an increase in thickness throughout the treatment. An opposite reaction occurred in the group A and B treated with oil/water lotion MB+LED and aqueous solution MB+LED, respectively. Statistically significant reductions on the thickness of the footpad and parasitic load were observed.

The scientific reports in PDT-treated animal models mentioned in this chapter show similar results to those reported in humans. In other words, PDT is capable to treat infected wounds reducing the parasitic load. In some cases, the complete disappearance of the parasite from tissue is achieved. Other aspect to highlight is its ability to inactivate both Old and New world *Leishmania* spp. Details of parameters from scientific studies using PDT on Old World and New World TL in murine models are described in table 1. However, treatment conditions of infected animals out of experimental controlled environment have not been described. Therefore, PDT has to become a more common procedure to be used in the clinical practice of Veterinary Medicine. It certainly has the unfulfilled potential to become a therapeutic alternative in veterinary medicine, and to help controlling the parasitic cycle in humans.


CG: control group / GA: group A / GB: group B

**Table 1.** Parameters used in PDT to the treatment of Old World tegumentary leishmaniasis and New World tegumentary leishmaniasis in murine models
