A survey of canine filarial diseases of veterinary and public health significance in India

Animal and Human Dirofilariasis in India and Sri Lanka: A Systematic Review and Meta-Analysis

Dirofilariasis is an emerging vector-borne tropical disease of public health importance that mainly affects humans and dogs. Dirofilaria immitis and D. repens are the two well-documented dirofilariasis-causing filarioid helminths of both medical and veterinary concerns in India and Sri Lanka. This systematic review and meta-analysis aimed to describe and summarize the current evidence of dirofilariasis prevalence and distribution in India and Sri Lanka. Interestingly, D. repens is reported to circulate in both dogs (prevalence of 35.8% (95% CI: 11.23-60.69)) and humans (97% of published case reports) in India and Sri Lanka, but D. immitis is reported to be present in the dog populations in India (prevalence of 9.7% (95% CI: 8.5-11.0%)), and so far, it has not been reported in Sri Lanka. This peculiar distribution of D. immitis and D. repens in the two neighbouring countries could be due to the interaction between the two parasite species, which could affect the pattern of infection of the two worm species in dogs and thus influence the geographical distribution of these two filarial worms. In medical and veterinary practice, histopathology was the most commonly used diagnostic technique (31.3%; 95% CI 2.5-60.2%). The low specificity of histopathology to speciate the various Dirofilaria spp. may lead to misdiagnosis. It was identified in this study that several regions of India and Sri Lanka have not yet been surveyed for dirofilariasis. This limits our understanding of the geographical distribution and interspecies interactions of the two parasites within these countries. Parasite distribution, disease prevalence, and interspecies interactions between the vectors and the host should be targeted for future research.

Heartworm adulticide treatment: a tropical perspective

Dirofilaria immitis (the canine heartworm) is widespread in the tropics, with prevalence surpassing 30% in high-risk areas. In addition to the suitable climatic conditions that favour mosquito abundance and filarial larva development, there is low compliance with the recommended year-round use of preventives in these transmission hotspots. This represents a major concern, considering that melarsomine (first-line heartworm adulticide) is unavailable in several tropical countries, resulting in the so-called slow-kill protocol being the only available adulticide treatment option. In this article, the members of TroCCAP (Tropical Council for Companion Animal Parasites) review the current distribution of heartworm in the tropics and the availability of melarsomine, and discuss alternatives for the management of heartworm infections in dogs.

First study on microscopic and molecular detection of Acanthocheilonema reconditum and Leishmania infantum coinfection in dogs in Southwest Colombia

Background and Aim

Canine vector-borne diseases represent an important issue for the welfare and health of animals, but also have great zoonotic potential. These diseases are caused by bacteria, nematodes such as filariae, and other parasites such as Leishmania spp. Given the difficulty in differentiating common microfilariae in dogs by microscopy and serological methods, molecular techniques such as polymerase chain reaction (PCR) and sequencing should be valuable for reaching a reliable diagnosis. This study aimed to use microscopy and PCR to identify the microfilarial species in dogs from Valle del Cauca, Colombia, and a possible association with Leishmania infantum parasites.

Materials and Methods

This study was conducted on 270 dogs from Pradera and Florida municipalities. Microfilariae were detected in dogs by optical microscopy and amplification with 5.8S-ITS2-28S. Species identification was achieved through the amplification of the gene cytochrome oxidase I (COX1).

Results

Microscopic detection of microfilariae was possible in 4.81% (13/270) of the dogs. In addition, by PCR of COX1 and Sanger sequencing of ITS2, Acanthocheilonema reconditum was identified as the circulating microfilarial species in 12 dogs, coinfecting with the species L. infantum (Leishmania donovani complex).

Conclusion

To the best of our knowledge, this is the first report on A. reconditum and L. infantum mixed infection in dogs in Colombia, particularly in the Valle del Cauca.

Cutaneous filarioid nematodes of dogs in the United States: Are they emerging, neglected, or underdiagnosed parasites?

Filarioid nematodes, which are vector-borne parasites of cosmopolitan distribution, of dogs are medically important. They are represented by species in which microfilariae were found to be circulating in the bloodstream (e.g., Dirofilaria sp., Acanthocheilonema sp., and Brugia sp.) or skin-dwelling (e.g., Cercopithifilaria sp. and Onchocerca sp.). Those species whose microfilariae are detected in blood have been extensively studied, especially Dirofilaria immitis, due to their clinical importance. In recent decades, there has been an increased interest by the scientific community in filarioid nematodes whose microfilariae are detected in the skin because of the zoonotic aspect of Onchocerca lupi. In the United States (US), although D. immitis has been considered the main filarioid infecting dogs, the intense animal movement and global canine filarioid diversity may indicate that the likely presence of cutaneous filarioid nematodes is more common than previously expected. Hence, a question remains: Are these canine filarioid nematodes emerging, neglected, or simply underdiagnosed in the US? In this review, we provide an overview of pertinent information that briefly summarizes the biology of the different canine filarioid nematode species, clinical signs associated with infections, and currently available diagnostic tools using molecular and microscopy-based methods and highlight knowledge gaps where research and surveillance efforts remain necessary. The data herein presented serve as an alert to the scientific community about the importance of filarioid nematodes infecting dogs other than D. immitis. Additionally, the zoonotic potential of several filarioid species reinforces the necessity of a proper diagnosis and the need for broader surveillance to understand their diversity and distribution, to highlight the potential introduction of certain species, and mitigate their establishment in the country and new animal and human cases.

First Report of Acanthocheilonema reconditum Outbreak in Canines with Clinical Signs of Anemia from Southwestern Colombia

Different nematodes affect canines, however Acanthocheilonema reconditum was considered mostly a non-pathogenic parasite. Climate change, animal migration, and other factors transformed the dynamics of vector-borne diseases, including filariasis. Since 2016, a sudden increase in the number of dogs with microfilaremia was reported by different veterinary centers in Cali, southwest Colombia. The objective of this study was to molecularly identify the etiologic agent of this filariasis outbreak detected in this city, using PCR−RFLP and evaluating dogs’ clinical signs. From 2018−2019, canine filariasis cases were prospectively evaluated after a microscopic test, recruiting 82 cases and 43 healthy controls from 2971 samples. Acanthocheilonema reconditum (Nematoda, Onchocercidae) was identified in 61.3% of the cases (49/82) by PCR−RFLP. Sanger sequencing of the 5.8S ribosomal RNA gene and internal transcribed spacer-2 fragment was additionally performed on seven cases, confirming A. reconditum in all of them. The filariasis cases are statistically associated with male dogs who have clinical signs of anemia, low levels of hemoglobin and hematocrit (p < 0.0001), and high levels of plasma proteins (p < 0.001). This emerging canine disease constitutes an important public health concern among veterinarians and active surveillance is advised to explore its zoonotic potential.

Characterization of the genetics and epidemiology of Brugia sp. in domestic dogs in Chad, Africa

Neglected tropical diseases pose a threat to domestic animal health, as domestic animals can serve as reservoirs for certain zoonotic parasitic infections, including Guinea worm (Dracunculus medinensis) and lymphatic filariasis. Surveillance for these parasites in domestic animals is needed to understand infection prevalence and transmission cycles, with the goal of instituting appropriate interventions. The goal of this research was to report our finding of Brugia sp. infection in dogs from Chad, Africa, and to characterize the genetics and epidemiology of the parasite. During a recent Chadian canine pathogen surveillance project, we identified Brugia sp. infections in a total of 46 out of 428 dogs (10.7%) sampled at three time points in 2019-2020. We found high levels of sequence similarity to B. malayi and B. pahangi based on amplification of 18S rRNA, 5.8S rRNA, and ITS-2 regions. Phylogenetic analysis of 18S rRNA gene sequences placed the Chadian Brugia sp. in a clade with other Brugia spp. but grouped it separately from both B. malayi and B. pahangi. Analysis of Hha I sequences showed the greatest similarity with B. patei, a parasite previously reported from dogs, cats, and wildlife hosts in Kenya. Epidemiologic analysis using generalized linear regression modeling found significantly higher odds of Brugia sp. detection among dogs in villages in southern Chad compared to those in the northern region. Further, within the northern region, there were higher odds of detection in the dry season, compared to the wet season, which is consistent with the ecology of a presumably mosquito-borne parasite. The same 428 dogs were tested for Dirofilaria immitis antigen using a commercial assay (IDEXX SNAP 4Dx) at the earliest time point of the study, with 119 dogs testing positive. However, no association was noted between Brugia infection and a dog being positive for Di. immitis antigen, with only seven of the 119 Di. immitis antigen-positive dogs being Brugia-positive. This is the first report of Brugia sp. in domestic dogs in Chad and additional research is needed to definitively identify the species present, elucidate transmission, and understand potential risks to canine and human health.

Canine filaria species in selected lymphatic filariasis endemic and non-endemic areas in Sri Lanka

Subperiodic brugian filariasis and dirofilariasis show a rising trend in Sri Lanka posing a threat to public health. As information was limited on canine filaria species in Sri Lanka, we studied the filaria parasites among dog populations in lymphatic filariasis (LF) endemic and non-endemic regions by microscopy and molecular methods. Thick blood smears (TBSs) were performed among 295 dogs presenting to veterinary clinics for surgical or sterilization procedures in Galle (LF endemic) and Mullaitivu (LF non-endemic) districts, of which 55.6% were positive for any microfilariae. We identified Dirofilaria repens (50.8%) and Brugia spp. (20.6%) by microscopy, which, included mono-infections (D. repens 35.3% and Brugia spp. 5%) and co-infections (15.6%). Infections in Galle and Mullaitivu were 61% and 44.9% respectively. The brugian filariasis rate was significantly higher among canines in LF endemic Galle district (29.9%) than in Mullaitivu (LF non-endemic) (1.1%) (P < 0.001), while D. repens infections were comparable in both districts. Genomic DNA extracted from 10% of microfilariae positive TBSs was amplified using pan-filarial primers targeting the internal-transcriber-spacer region-2 (ITS-2). Sequencing of amplicons confirmed the presence of D. repens (89.28%), Brugia pahangi (7.14%) and B. malayi (3.57%) infections. The phylogeny constructed and analysed in MEGA X indicated genetic variability among D. repens and B. pahangi isolates from Sri Lanka. With this study, we were able to report B. pahangi infections for the first time in Sri Lanka.

A study on canine dirofilariasis in selected areas of Sri Lanka

Objectives

Canine dirofilariasis is a mosquito borne zoonotic filarial parasitic disease caused by Dirofilaria species. In Sri Lanka, human dirofilariasis is endemic and well documented. Even though canine dirofilariasis is an established infection among dog populations in Sri Lanka, the prevalence and risk factors were not documented in Kanthale divisional secretariat, Eastern Province of Sri Lanka. Therefore, the main objective of this study is to determine the prevalence of dirofilariasis and to identify the exposure-related risk factors in dogs using an interviewer administered questionnaire in Kanthale divisional secretariat.

Results

Out of 162 blood samples collected from dogs, 47.5% (n = 77/162) were positive for the presence of microfilariae by direct smear. Of 162 samples 58.6% (n = 95/162) were molecularly identified as D. repens. Species-specific primer pair DIR3/DIR4 that amplified 5S rRNA was used. The current study observed a significant association between mongrels and canine dirofilariasis (p = 0.049), where 61.3% (n = 95) out of 155 mongrels showed PCR positivity. This study showed no significant association between the occurrence of dirofilariasis and the age, sex, rearing method, presence or absence of skin rash, and stray or domestic dogs. Dirofilaria immitis was not identified in direct smear test and PCR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-06024-0.

Occurrence of Dirofilaria immitis in Stray Dogs from Nepal

BACKGROUND

Nematodes of the genus Dirofilaria are widespread vector-borne helminths (VBH) of veterinary relevance. Dirofilariosis caused by D. immitis is frequently diagnosed in dogs often showing a severe clinical condition known as heartworm disease. Assessing the distribution pattern of canine dirofilariosis is pivotal to undertake appropriate control measures and define the risk of infection in animals and humans. This study provides original data on the occurrence of D. immitis in naive stray dogs from Nepal.

METHODS

An epidemiological study was performed on stray dogs from Siddharthanagar, Lumbini region, Nepal. Alive animals were blood sampled and examined for microfilariae using direct microscopy, buffy coat centrifugation and modified Knott's method. In addition, hematobiochemical parameters, including packed cell volume (PCV), alanine aminotransferase (SGPT), aspartate aminotransferase (SGOT), alkaline phosphate (ALP), creatinine, blood urea nitrogen (BUN), urea and total protein were analysed, along with a clinical scoring (body temperature and respiratory rate). During the observation period, data on autopsies performed on stray dogs showing canine heartworm disease were also included.

RESULTS

The overall prevalence of D. immitis in both alive and necropsied dogs was 22.49% (38/169). Out of 150 alive dogs, 29 (19.3%) were positive for D. immitis microfilariae. The prevalence of the infection varied according to the technique used, ranging from 16.0 to 19.3% based on direct blood smear microscopy and modified Knott's technique, respectively. The infection rate was significantly higher (p < 0.05) in dogs aging more than 3 years. A positive correlation was observed between SGPT and SGOT and the presence of microfilariae (p < 0.05). Among the 19 dead stray dogs, 9 animals showed adult D. immitis nematodes.

CONCLUSION

Results of this survey account for the presence of D. immitis in stray dogs from Nepal, thus supporting the existence of a local transmission cycle of diroflariosis in the region. Further investigations are warranted to accurately define the prevalence of the infection in the canine population and to undertake appropriate control measures to reduce the burden on the infection in dogs and, accordingly, the risk of transmission to humans.

Molecular Approach for the Diagnosis of Blood and Skin Canine Filarioids

The zoonotic Onchocerca lupi and tick-transmitted filarioids of the genus Cercopithifilaria remain less well known due to the difficulties in accessing to skin samples as target tissues. Here, we proposed a molecular approach reliying on multiplex qPCR assays that allow the rapid identification of filarioids from canine blood, skin, and tick samples. This includes two newly developed duplex qPCR tests, the first one targeting filarial and C. grassii DNA (CanFil-C. grassii). and the second qPCR assay designed for the detection of Cercopithifilaria bainae and Cercopithifilaria sp. II DNAs (C. bainae-C.spII). The third one is a triplex TaqMan cox 1 assay targeting DNA of blood microfilariae (e.g., Dirofilaria immitis, Dirofilaria repens and Acanthocheilonema reconditum). The novel duplex qPCRs developed were validated in silico and by screening of known DNA collection. The qPCR assays were also used for screening the blood and tick samples of 72 dogs from Algeria. This allowed the identification of canine filariasis infection with 100% of specificity and 89.47% and 100% of sensitivity from naturally infected blood and tick samples, respectively. The prevalences of 26.39% for D. immitis and 5.56% for both D. repens and A. reconditum were reported in blood and tick samples. Cercopithifilaria DNAs were detected only in tick samples, with a prevalence of 4.17% and 5.56% for C. bainae and Cercopithifilaria sp. II, respectively. Co-infections were diagnosed in 6.94% and 13.89% of blood and tick samples, respectively. Whereas all samples were negative for C. grassii DNA. The use of engorged ticks instead of blood and skin samples could be an easier option for the surveillance of all canine filarioids herein investigated. The multiplex qPCR assays herein validated were shown to be useful in the detection of filarial co-infections by overcoming sequencing of positive samples.

Keds, the enigmatic flies and their role as vectors of pathogens

Hippoboscid flies (Diptera: Hippoboscidae), commonly known as keds or louse flies, have been for long time overlooked by the scientific community, and their vector role of infectious agents to humans and domestic animals has been scantly investigated. This is partly due to the fact that the host range for most species is primarily restricted to wildlife, being rarely reported on domestic animals and humans. This led to a scarce scientific knowledge about their biology, ecology, behaviour, epidemiology as well as vector competence. However, the life history of some hippoboscid species, e.g., Melophagus ovinus, Lipoptena cervi and Hippobosca equina, suggests that these ectoparasites are important candidates to vector infectious disease agents (e.g., Rickettsia spp., Borrelia spp., Bartonella spp., Anaplasma phagocytophilum, Theileria ovis). Indeed, the peculiar biological and behavioural traits (i.e., obligatory blood sucking and reproductive physiology) of many ked species make them a suitable pabulum for pathogen's multiplication and for their transmission to receptive hosts. Therefore, studies focusing on the ked bio-ecological aspects as well as on their vector role are advocated along with the control of keds affecting different animal species. This review discusses current information on keds, highlighting their importance as vectors of pathogens of medical and veterinary concern to all animal species, with a special focus on mammals.

Molecular Analysis of Canine Filaria and Its Wolbachia Endosymbionts in Domestic Dogs Collected from Two Animal University Hospitals in Bangkok Metropolitan Region, Thailand

Canine filariasis is caused by several nematode species, such as Dirofilaria immitis, Dirofilaria repens, Brugia pahangi, Brugia malayi, and Acanthocheilonema reconditum. Zoonotic filariasis is one of the world's neglected tropical diseases. Since 2000, the World Health Organization (WHO) has promoted a global filarial eradication program to eliminate filariasis by 2020. Apart from vector control strategies, the infection control of reservoir hosts is necessary for more effective filariasis control. In addition, many studies have reported that Wolbachia is necessary for the development, reproduction, and survival of the filarial nematode. Consequently, the use of antibiotics to kill Wolbachia in nematodes has now become an alternative strategy to control filariasis. Previously, a case of subconjunctival dirofilariasis caused by Dirofilaria spp. has been reported in a woman who resides in the center of Bangkok, Thailand. Therefore, our study aimed to principally demonstrate the presence of filarial nematodes and Wolbachia bacteria in blood collected from domestic dogs from the Bangkok Metropolitan Region, Thailand. A total of 57 blood samples from dogs with suspected dirofilariasis who had visited veterinary clinics in Bangkok were collected. The investigations for the presence of microfilaria were carried out by using both microscopic and molecular examinations. PCR was used as the molecular detection method for the filarial nematodes based on the COI and ITS1 regions. The demonstration of Wolbachia was performed using PCR to amplify the FtsZ gene. All positive samples by PCR were then cloned and sequenced. The results showed that the filarial nematodes were detected in 16 samples (28.07%) using microscopic examinations. The molecular detection of filarial species using COI-PCR revealed that 50 samples (87.72%) were positive; these consisted of 33 (57.89%), 13 (22.81%), and 4 (7.02%) samples for D. immitis, B. pahangi, and B. malayi, respectively. While the ITS1-PCR showed that 41 samples (71.93%) were positive-30 samples (52.63%) were identified as containing D. immitis and 11 samples (19.30%) were identified to have B. pahangi, whereas B. malayi was not detected. Forty-seven samples (82.45%) were positive for Wolbachia DNA and the phylogenetic tree of all positive Wolbachia was classified into the supergroup C clade. This study has established fundamental data on filariasis associated with Wolbachia infection in domestic dogs in the Bangkok Metropolitan Region. An extensive survey of dog blood samples would provide valuable epidemiologic data on potential zoonotic filariasis in Thailand. In addition, this information could be used for the future development of more effective prevention and control strategies for canine filariasis in Thailand.

Systematic Review of Lesser Known Parasitoses: Maxillofacial Dirofilariasis

BACKGROUND

Dirofilariasis is an endemic disease in tropical and subtropical countries caused by about 40 different species of dirofilari. Dirofilariasis of the oral cavity is extremely rare and is usually seen as mucosal or submucosal nodules. We also present a case of dirofilariasis of the mandibular third molar region submucosally in a 26 year old male patient.

PURPOSE

To identify, enlist and analyze the cases of dirofilariasis in maxillofacial region reported worldwide so as to understand the clinical presentation and encourage the consideration of helminthic infections as a possible differential diagnosis in maxillofacial swellings.

METHODS

Two authors KC and SK independently searched the electronic database of PUBMED, OVID, Google Scholar and manual search from other sources. A general search strategy was planned and anatomic areas of interest identified. The search was made within a bracket of 1 month by the independent authors KC and SK who assessed titles, abstracts and full texts of articles based on the decided keywords. The final selection of articles was screened for the cases that were reported in the maxillofacial region including the age, gender, site of occurrence and region of the world reported in. A geographic distribution of the reported cases was tabulated.

RESULTS

A total number of 265, 97, 1327, 3 articles were identified by PubMed, Ovid, GoogleScholar and manual search respectively. The final articles were manually searched for duplicates and filtered according to the inclusion/exclusion criteria which led to a final list of 58 unique articles that were included in the study. In total 99 cases were identified.

CONCLUSION

Although intraoral dirofilarial infections are extremely uncommon, it should be considered in the differential diagnosis of an intraoral or facial swelling that does not completely respond to routine therapy especially in patients from endemic areas.

Molecular investigation of vector-borne parasitic infections in dogs in Northeast India

BACKGROUND

Information on the status of vector-borne pathogens among canines in Northeast India is lacking, particularly for the states of Mizoram and Tripura close to the Myanmar border. Blood samples collected from 130 dogs, 80 from Mizoram and 50 from Tripura, were examined in this study.

METHODS

Polymerase chain reaction (PCR) was performed for filariid worms, Babesia, Hepatozoon, Ehrlichia and Anaplasma spp. and DNA sequencing was then carried out to identify pathogens at the species level.

RESULTS

Vector-borne pathogens were detected in 52% (68/130) of the sampled dogs. The most prevalent pathogen was Babesia gibsoni detected in 56/130 (43%) dogs, followed by Hepatozoon canis in 50/130 (38%), Anaplasma platys in 4/130 (3%), B. vogeli in 4/130 (3%), Acanthochelionema reconditum in 3/130 (2%) and Dirofilaria immitis in 2/130 (2%). Forty-four dogs (34%) were co-infected with two or more pathogens. The most common co-infection observed was with B. gibsoni + H. canis (34%) followed by triple-infection with B. gibsoni + H. canis + A. platys (3%), and B. gibsoni + B. vogeli + H. canis (3%). The infection rate was higher in Mizoram (58%) than in Tripura (44%).

CONCLUSIONS

The high prevalence of infection in the studied dog population, especially with B. gibsoni and H. canis, indicates that vector-borne diseases pose a serious threat to the health of dogs in this area of Northeast India. Prevention of vector-borne diseases by using topical acaricides and heartworm preventative treatment would be of great benefit for reducing the threat of vector-borne diseases in the study area.

Epizootiological observations on canine microfilaremia in Gujarat state, India

Aim

The present investigation was conducted to study the prevalence of microfilaremia in dogs in Gujarat.

Materials and Methods

A total of 418 adult dogs aged between 2 and 14 years with signs of weakness and non-specified complaints, presented at TVCC, Deesa (North Gujarat), Nandini Veterinary Hospital, Surat (South Gujarat), and Private Clinics, Ahmedabad (Central Gujarat), were included in the present investigation for studying the prevalence of microfilaremia from July 2016 to May 2017.

Results

A total of 418 dogs were screened, of which 33 were found positive for circulating microfilariae with the prevalence rate of 7.89% in the population. Among microfilaremic dogs, the finding of microfilariae of Dipetalonema (Acanthocheilonema) reconditum was more common (23 cases; 69.69%) than Dirofilaria immitis (10 cases; 30.30%) making their prevalence in the population of 418 dogs as 5.50% and 2.39%, respectively. Breed-wise distribution of microfilaremic dogs revealed that 12 (36.36%), 8 (24.24%), 5 (15.15%), 4 (12.12%), 2 (6.06%), 1 (3.03%), and 1 (3.03%) cases were observed in Pomeranian, non-descript, German Shepherd, Labrador, Great Dane, Lhasa Apso, and Pug dogs, respectively. Of 10 cases of D. immitis, 5, 2, 2, and 1 were observed in Pomeranian, Labrador, non-descript, and Great Dane dogs, respectively. Cases of Dipetalonema reconditum were highest in Pomeranian (7), followed by non-descript (6), German Shepherd (5), Labrador (2), Great Dane (1), Lhasa Apso (1), and Pug (1). Age-wise distribution recorded significantly (p≤0.01) higher number of cases in adult dogs (4-14 years) for D. immitis (30.30%) and D. reconditum (39.39%). Sex-wise distribution of microfilaremic dogs showed that male (22/33, 66.66%) was more predisposed to microfilaremia rather than females (11/33, 33.34%). It is apparent from the study that the number of dogs with microfilaremia due to D. reconditum was significantly (p≤0.01) higher than that of D. immitis.

Conclusion

The present study revealed that microfilaremia due to D. immitis and D. reconditum is prevalent in the state of Gujarat. The infection with D. immitis was associated with severe lung and cardiac pathological manifestations.

A preliminary survey of filarial parasites in dogs and cats in Sri Lanka

Human brugian filariasis has re-emerged in Sri Lanka after a quiescent period of four decades. This study investigated the prevalence of canine and feline filarial parasites in three localities with human sub-periodic brugian filariasis, in order to determine their potential reservoir status. All reachable dogs and cats, both stray and domestic, within a 350m radius of an index case of brugian filariasis in three locations (Madampe, Wattala and Weliweriya) were screened for microfilariae using Giemsa stained thick blood smears. A representative sample of canine and feline blood samples positive for Brugia spp. microfilariae by microscopy, from each of the three locations, were further analyzed by PCR with specific primers for internal transcribed spacer region 2 (ITS2) of the ribosomal DNA. A total of 250 dogs and 134 cats were screened. The overall microfilaraemia rates were high among both dogs (68.8%) and cats (47.8%). The prevalence of microfilaraemia was significantly higher among dogs than cats (p<0.05). Two filarial species were identified based on morphology of microfilariae: Dirofilaria (Nochtiella) repens (dogs, 54.4% and cats, 34.3%) and Brugia spp. (dogs, 51.6% and cats, 30.6%). PCR analysis of canine (n = 53) and feline (n = 24) samples elicited bands in the region of 615bp, which confirmed Brugia malayi infection. Co-infection with D.(N.) repens was detected by PCR with an additional band at 484bp, in 36 canine and 17 feline samples. Overall microfilaraemia rates of dogs (81.8%) and cats (75%) in Madampe (rural) were significantly higher than in urbanized Wattala (dogs, 62.4% and cats, 26.0%) (p<0.05). High rates of zoonotic filarial infections strongly implicate dogs and cats as potential reservoirs for human dirofilariasis and brugian filariasis in Sri Lanka.

Whether Dirofilaria repens parasites from South India belong to zoonotic Candidatus Dirofilaria hongkongensis (Dirofilaria sp. hongkongensis)?

The canine and zoonotic dirofilarioses are arthropod-borne parasitic infections caused by nematodes of the genus Dirofilaria, infecting canines, felines and humans throughout the world. Dirofilaria repens was considered as the most common cause of human dirofilariosis in Kerala. In the present study, molecular characterization of Dirofilaria isolates causing dirofilariosis in humans, dogs and jackal from Kerala, South India was undertaken by performing sequence and phylogenetic analysis based on cytochrome oxidase subunit I (COI) gene. The live worms from swellings/ nodules in subconjunctiva or subcutaneous tissue or scrotum were recovered from humans (n = 3), dogs (n = 4) and one jackal. The PCRs targeting a repetitive fragment, 18S rRNA and COI genes yielded products of ~246 bp, ~875 bp and ~350 bp respectively in all the samples. The sequence analysis of 18S rRNA gene revealed the closest identity (98 to 99%) with an already published sequence of D. repens isolated from a human in Japan. However, based on the sequence and phylogenetic analysis of partial sequences of COI gene, the Dirofilaria infecting both animals (dogs, jackal) and humans native to Kerala, South India were identified as genetically conserved and closely related to Dirofilaria sp. hongkongensis. Hence, the results of the present study suggested the existence of Candidatus Dirofilaria hongkongensis (Dirofilaria sp. hongkongensis) in Kerala, South India causing zoonotic filariosis in canines and humans.

Canine filariasis in the Amazon: Species diversity and epidemiology of these emergent and neglected zoonoses

Dirofilaria immitis and Acanthocheilonema reconditum are common parasites in dogs but have also been reported parasitizing humans. The differential diagnosis and epidemiological evaluation of these zoonoses are important to the development of efficient public health policies and control strategies. The purpose of this study was to carry out an epidemiological survey by using molecular methods for the specific identification of filarid parasites of domestic dogs in the Marajó mesoregion, State of Pará (PA), Brazil. A total of 418 canine blood samples from Marajó mesoregion (Northern Brazil) were collected, submitted to DNA extraction, polymerase chain reaction (PCR) with “pan filarial” primer, subsequent sequencing and sequence analysis using BLASTn software comparison with previously deposited sequences in GenBank. After that, a phylogenetic analysis by Maximum Parsimony was performed to aid the specific diagnosis. The obtained sequences showed the occurrence of 9 (2.15%) dogs infected with D. immitis and 30 (7.18%) by A. reconditum, with a confidence interval of 95%, there were no cases of co-infection. We observed that male dogs were more likely to D. immits and A. reconditum infection. However, age was not significant to both infections. This study reports for the first time the occurrence of A. reconditum in the northern region of Brazil and confirmed the presence of D. immitis in the Marajó mesoregion.

Nodular presentation of Dirofilaria repens infection in a cat mimicking a fibrosarcoma

A cat with multiple subcutaneous nodules suggesting a soft tissue sarcoma by physical and computed tomographic examination was diagnosed as being affected by subcutaneous filariosis based on cytologic and ultrasonographic assessments. Nodules were surgically removed and extracted nematodes were identified by PCR as Dirofilaria repens. Furthermore, DNA of Dipetalonema dracunculoides (syn. Acantocheilonema dracunculoides) was detected by PCR, with no evidence of circulating microfilariae. To the best of the authors' knowledge, this represents the first report describing adults of D repens in multiple subcutaneous nodules in a cat. Cytopathologic examination allowed characterization of the parasitic nature of the nodules. Veterinary practitioners should be aware of the possible nodular presentation of D repens in cats and should include D repens in the differential diagnosis of subcutaneous neoformations in the cat.

Identification of microfilaria in a mammary mass aspirate from a female dog

A filarial nematode larva (microfilaria) was found in an aspirate of a mammary mass from a dog imported to Saskatchewan from Myanmar. This was an unusual location for a microfilaria and numerous filarial nematodes infecting dogs in Asia had to be considered. This report describes the laboratory diagnosis of canine heartworm disease in this dog.

Occult Dirofilariosis in Dogs of North Eastern Region in India

BACKGROUND

The North Eastern Region in India is endemic for canine heartworm disease but in clinics accurate diagnosis is some times difficult. The aim of the present study was to determine the prevalence of occult infections for heartworm disease in canine in two geographical regions of North Eastern India.

METHODS

A total of 782 numbers of three categories of dogs namely, working dogs of military and paramilitary forces, pet dogs and stray dogs were screened for the presence of heartworm infection from August 2011 to July, 2012 in Guwahati (Assam) and Aizawl (Mizoram). Conventional, immunological and molecular techniques were followed for this epidemiological study. The criteria to determine the occult heartworm cases were based on the differences between heartworm positive cases in PCR test and antigen ELISA test.

RESULTS

The findings revealed an overall 22.69 percent occult case. The working dogs had highest prevalence (60%) followed by pet (29.16%) and stray dogs (17.75%).

CONCLUSION

The highest percentage of occult heartworm infection was present in working dogs maintained under military or paramilitary forces.

Canine vector-borne infections in Mauritius

Background

Canine vector-borne diseases have a worldwide distribution, but to the best of our knowledge, no research has been carried out to evaluate their presence on the Indian Ocean island of Mauritius. An investigation into canine vector-borne infections was conducted in dogs (n = 78) resident at an animal shelter in Port Louis, Mauritius using a combination of traditional microscopy and serological methods.

Methods

Ticks were manually collected from the stray dog population for identification as well as for quantifying tick burdens. Blood was also collected from each dog via either the jugular vein or the cephalic vein, and was stored in EDTA tubes. The stored blood was then used to measure PCV values, make blood smears for the identification of parasites, and used for serological testing of vector-borne disease.

Results

A total of 178 ticks were collected from 52 dogs and identified as Rhipicephalus sanguineus (175/178) or Amblyomma variegatum (3/178). Twenty-six (33%; 95% CI 23, 45) dogs were seropositive for Ehrlichia spp., and 12 (15%; 95% CI 8, 25) for Anaplasma spp., Dirofilaria antigen was detected in 14 (18%; 95% CI 10, 28), and nine (12%; 95% CI 5, 21) dogs had Hepatozoon canis gamonts observed in blood films during microscopic examination. Eleven (14%; 95% CI 7, 24) dogs were co-infected with two pathogens. Borrelia burgdorferi antibodies were not detected in any dogs.

Conclusions

Infection with these pathogens had no significant effect on the packed cell volume (PCV), but high tick burdens were significantly associated with the presence of a tick-borne pathogen. This is the first study of its kind on the dog population in Mauritius and demonstrates the presence of previously undocumented canine vector-borne infections on the island. The relatively high proportion of infected dogs within the study should alert clinicians to the presence of canine vector-borne diseases on the island of Mauritius.

Prevalence and molecular epidemiological data on Dirofilaria immitis in dogs from Northeastern States of India

The aim of the present study was to determine the prevalence of Dirofilaria immitis in stray, pet, and working dogs (n = 413, 266, and 103, resp.) from Guwahati (Assam) and Aizawl (Mizoram), areas located in two Northeastern States of India. Diagnostic methods applied were microscopy (wet film and Knott's concentration technique), immunological test (Ag ELISA by SNAP 4Dx ELISA kit), and molecular tools (polymerase chain reaction and sequencing), which evidenced 11.38, 18.03, and 13.93% of positive animals, respectively. No significant differences were observed by area (18.23% versus 17.68%) nor by sex (18.1% versus 17.9%), whereas stray dogs proved more infected than other groups (P < 0.05). ELISA test evidenced an overall 22.69% of occult infections, mainly in working dogs (60%), and molecular techniques detected Dirofilaria (Nochtiella) repens in 4 stray dogs from Guwahati. Characterization of D. immitis isolates for ITS-2 region showed close identity with South Asian isolates.

Subcutaneous Dirofilaria repens infestation in non-descript canines

Dirofilaria repens is a filarial nematode which cause subcutaneous dirofilariosis. Dogs, foxes and cats are the definitive hosts and principal reservoirs of the parasite. We report cases of D. repens infestation in non-descript canines from Goa, India. The nematodes were enclosed within fibrous capsule or freely present in the tunica vaginalis of the testes, in sub-cutaneous tissue of foreleg and body cavity. The parasite showed well-developed thick multilayered cuticular ridges in the outermost layer, followed by transverse smooth muscles striations.

Canine filarial infections in a human Brugia malayi endemic area of India

A very high prevalence of microfilaremia of 42.68 per cent out of 164 canine blood samples examined was observed in Cherthala (of Alappuzha district of Kerala state), a known human Brugia malayi endemic area of south India. The species of canine microfilariae were identified as Dirofilaria repens, Brugia malayi, and Acanthocheilonema reconditum. D. repens was the most commonly detected species followed by B. pahangi. D. immitis was not detected in any of the samples examined. Based on molecular techniques, microfilariae with histochemical staining pattern of "local staining at anal pore and diffuse staining at central body" was identified as D. repens in addition to those showing acid phosphatase activity only at the anal pore. Even though B. malayi like acid phosphatase activity was observed in few dogs examined, they were identified as genetically closer to B. pahangi. Hence, the possibility of dogs acting as reservoirs of human B. malayi in this area was ruled out.

Adult of Dirofilaria repens in a dog with recurrent multiple subcutaneous nodular lesions

Subcutaneous dirofilariosis is a zoonosis parasitizing the dog, transmitted by Culicidae mosquitoes. An increasing number of new cases have been reported both in dogs and in humans all over the world. The aim of this work was to describe an uncommon case of recurrent multiple subcutaneous nodules by Dirofilaria repens in a 2-year-old dog. Surgical excision of two nodules on both hind limbs revealed a single thread-like live nematode and multiple parasite fragments, respectively. The parasite was morphologically identified as an adult female of D. repens. Haematoxylin-eosin tissue sections of nodules revealed a diffuse pyogranulomatous angiocentric dermatitis with an intense eosinophilic infiltrate throughout the dermis. One month post-surgery, a new nodular lesion was detected on the right thigh and resolved spontaneously in a few weeks. During the following 3 months, two other nodules were briefly noted both on the right hip and on the left side of the chest. The dog was periodically treated with milbemycin oxime and praziquantel, starting a week before the appearance of the first nodule. Microfilariae were not detected neither in the bloodstream nor in fine-needle aspirates at any time, and the diagnosis was made only after surgery. Practitioners should consider dirofilariosis in the differential diagnosis of subcutaneous swellings, especially if they have a recurrent behaviour, previously described in humans but not in dogs.

Indigenous Dirofilaria immitis in Bangladesh

Dirofilaria immitis is a parasite of domestic and wild canids and felids in tropical, subtropical and temperate regions throughout the world. The canine heartworm (D. immitis) is the causative agent of canine and feline cardiopulmonary dirofilariasis. This parasite is known to cause a zoonotic disease, namely human pulmonary dirofilariasis. D. immitis is known to be endemic in several South and Southeast Asian countries (e.g. India and Malaysia), but there has previously been no information about the presence of this pathogen in Bangladesh. We present a case of canine dirofilariasis caused by D. immitis in rural southeastern Bangladesh. A male filaroid nematode (95 mm in length and 1.94 mm in width) was identified in the heart of a dog. Species classification was performed by microscopy and molecular tools. Sequence analysis revealed a 100 % identity within the mitochondrial cytochrome c oxidase I (CO1) gene to two Chinese and one Australian D. immitis samples. Usually, dogs stay outside overnight with a high risk to get infected with D. immitis via nocturnal mosquito vectors, which may lead to high prevalences of this pathogen in the canine population and thus increase the risk of human infections with this neglected parasitic disease.

Vector-borne helminths of dogs and humans in Europe

Presently, 45% of the total human population of Europe, as well as their domestic and companion animals, are exposed to the risk of vector-borne helminths (VBH) causing diseases. A plethora of intrinsic biological and extrinsic factors affect the relationship among helminths, vectors and animal hosts, in a constantly changing environment. Although canine dirofilarioses by Dirofilaria immitis and Dirofilaria repens are key examples of the success of VBH spreading into non-endemic areas, another example is represented by Thelazia callipaeda eyeworm, an emergent pathogen of dogs, cats and humans in several regions of Europe. The recent finding of Onchocerca lupi causing canine and human infestation in Europe and overseas renders the picture of VBH even more complicated. Similarly, tick-transmitted filarioids of the genus Cercopithifilaria infesting the skin of dogs were recently shown to be widespread in Europe. Although for most of the VBH above there is an increasing accumulation of research data on their distribution at national level, the overall impact of the diseases they cause in dogs and humans is not fully recognised in many aspects. This review investigates the reasons underlying the increasing trend in distribution of VBH in Europe and discusses the diagnostic and control strategies currently available. In addition, this article provides the authors' opinion on some topics related to VBH that would deserve further scientific investigation.

A novel Dirofilaria species causing human and canine infections in Hong Kong

Dirofilariasis is globally the commonest manifestation of zoonotic filariasis. We report the detection of a novel canine species causing human and canine dirofilariasis in Hong Kong. Three human cases occurring over 10 months were identified, one presenting with cervical lymphadenopathy, one with an abdominal subcutaneous mass, and one with a subconjunctival nodule. Transected worms recovered from the resected abdominal subcutaneous mass were morphologically compatible with Dirofilaria. The cox1 gene sequences of the three human isolates were identical; however, they were only 96.2% and 89.3% identical to the cox1 gene of Dirofilaria repens and Dirofilaria immitis, respectively. Sequencing of the 18S-ITS1-5.8S gene cluster was successful in the intact worm, and the nucleotide sequences were 94.0% and 94.9% identical to those of D. repens and D. immitis, respectively. Screening of the blood samples from 200 dogs and 100 cats showed the presence of the novel Dirofilaria species in 3% (6/200) of the dogs' but none of the cats' blood samples. Nucleotide sequences of the cox1 gene and 18S-ITS1-5.8S gene clusters of the dogs' samples were identical to those in the human samples. The sera of canines infected by this novel Dirofilaria species were negative when tested with the SNAP 4Dx D. immitis detection kit, except in the case of dogs with a mixed infection with D. immitis as detected by PCR. The results from this study suggest that this novel Dirofilaria species is a cause of filarial infection in humans and dogs in Hong Kong. We propose to name this Dirofilaria species "Candidatus Dirofilaria hongkongensis."

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Canine vector-borne disease pathogens in dogs from south-east Queensland and north-east Northern Territory

OBJECTIVES

To determine the prevalence of canine vector-borne diseases (CVBD: Babesia spp., Anaplasma spp., Ehrlichia spp., haemotropic mycoplasmas and Hepatozoon) in Australian dogs; namely, dogs from pounds in south-east Queensland and an indigenous Aboriginal community in the north-east of the Northern Territory.

DESIGN AND PROCEDURE

Blood samples were collected from 100 pound dogs and 130 Aboriginal community dogs and screened for the CVBD pathogens using polymerase chain reaction (PCR). All positive PCR products were sequenced for species confirmation.

RESULTS

In total, 3 pound dogs and 64 Aboriginal community dogs were infected with at least one CVBD pathogen. Overall, B. vogeli was detected in 13 dogs, A. platys in 49, M. haemocanis in 23, Candidatus Mycoplasma haematoparvum in 3 and C. M. haemobos in 1 dog. Co-infections were detected in 22 Aboriginal community dogs.

CONCLUSIONS

This study found B. vogeli, A. platys and haemotropic mycoplasma infections to be common in dogs in subtropical and tropical areas of Australia. This study also reports for the first time the prevalence and genetic characterisation of haemotropic mycoplasmas in dogs in Australia.

Molecular evidence of Rickettsia felis infection in dogs from Northern Territory, Australia

The prevalence of spotted fever group rickettsial infection in dogs from a remote indigenous community in the Northern Territory (NT) was determined using molecular tools. Blood samples collected from 130 dogs in the community of Maningrida were subjected to a spotted fever group (SFG)-specific PCR targeting the ompB gene followed by a Rickettsia felis-specific PCR targeting the gltA gene of R. felis. Rickettsia felis ompB and gltA genes were amplified from the blood of 3 dogs. This study is the first report of R. felis infection in indigenous community dogs in NT.

Macrocyclic lactones and Dirofilaria immitis microfilariae

Although there has been extensive veterinary focus on both the effectiveness of macrocyclic lactones for heartworm prevention in dogs and their adulticidal effects, little attention has been directed to their effects on heartworm microfilariae. With routine use of macrocyclic lactones, in some cases knowingly, in dogs with existing heartworm infections, veterinarians should recognize the benefits, and possible complications, arising from this behavior. Macrocyclic lactones remain our only class of heartworm prevention available, and preserving their effectiveness is critical. Drugs in this class share common traits: there are currently no Food and Drug Administration-approved microfilaricides in the US marketplace, but because all macrocyclic lactones have microfilaricidal properties (to varying degrees), they are widely used by veterinarians for this purpose. Originally formulated to be used in dogs without patent heartworm infections, all have been demonstrated as safe to use at label doses, and higher, in microfilaremic dogs. All of the product labels indicate that dogs should be tested for heartworm infection before starting preventive therapy. Although microfilaricidal, microfilariae reduction may take many months to occur, and some dogs may never clear. The effects of macrocyclic lactones on the numbers of circulating microfilariae may be due to several different underlying causes (i.e., direct effect on the nervous system, affecting stages found in the uterus of the female worms), but the details of all mechanisms by which microfilariae are killed and/or cleared in dogs treated with macrocyclic lactones have not yet been fully elucidated. Some 10% to 20% of heartworm-infected dogs that begin monthly heartworm preventive treatment without adulticide therapy will have the continued and persistent presence of circulating microfilariae, and the concern is that this may be selecting for resistance to these molecules. The veterinary literature now includes evidence of increased genotypic homozygosity in specific dogs in one area of the country for a marker gene associated with macrocyclic lactone resistance in nematodes of ruminants. This article will review the biology of microfilariae, as well as the evolution of diagnostic testing for heartworm infection. The effects of macrocyclic lactones on microfilaria behavior and survival will be discussed, as well as the use and effects of macrocyclic lactones in microfilaremic dogs, with or without adulticide treatment. The effect of doxycycline on heartworm microfilariae, optimal testing methodologies, and verification of effective clearance of microfilariae after adulticide treatment and microfilaricidal therapy so that dogs do not remain a potential source of infection for other dogs are all covered.

Hippobosca longipennis--a potential intermediate host of a species of Acanthocheilonema in dogs in northern India

Background

Hippobosca longipennis (the 'dog louse fly') is a blood sucking ectoparasite found on wild carnivores such as cheetahs and lions and domesticated and feral dogs in Africa, the Middle East and Asia, including China. Known as an intermediate host for Acanthocheilonema dracunculoides and a transport host for Cheyletiella yasguri, it has also been suggested that H. longipennis may be a vector for other pathogens, including Acanthocheilonema sp.? nov., which was recently reported to infect up to 48% of dogs in northern India where this species of fly is known to commonly infest dogs. To test this hypothesis, hippoboscid flies feeding on dogs in Ladakh in northern India were collected and subjected to microscopic dissection.

Results

A total of 12 infective larvae were found in 10 out of 65 flies dissected; 9 from the head, 2 from the thorax and 1 from the abdomen. The larvae averaged 2, 900 (± 60) μm in length and 34 (± 5) μm in width and possessed morphological features characteristic of the family Onchocercidae. Genetic analysis and comparison of the 18S, ITS-2, 12S and cox-1 genes confirmed the identity of the larvae as the Acanthocheilonema sp.? nov. reported in dogs in Ladakh.

Conclusion

This study provides evidence for a potential intermediate host-parasite relationship between H. longipennis and the canine Acanthocheilonema sp.? nov. in northern India.

A survey of canine tick-borne diseases in India

Background

There are few published reports on canine Babesia, Ehrlichia, Anaplasma, Hepatozoon and haemotropic Mycoplasma infections in India and most describe clinical disease in individual dogs, diagnosed by morphological observation of the microorganisms in stained blood smears. This study investigated the occurrence and distribution of canine tick-borne disease (TBD) pathogens using a combination of conventional and molecular diagnostic techniques in four cities in India.

Results

On microscopy examination, only Hepatozoon gamonts were observed in twelve out of 525 (2.3%; 95% CI: 1.2, 4) blood smears. Using polymerase chain reaction (PCR), a total of 261 from 525 dogs (49.7%; 95% CI: 45.4, 54.1) in this study were infected with one or more canine tick-borne pathogen. Hepatozoon canis (30%; 95% CI: 26.0, 34.0) was the most common TBD pathogen found infecting dogs in India followed by Ehrlichia canis (20.6%; 95% CI: 17.2, 24.3), Mycoplasma haemocanis (12.2%; 95% CI: 9.5, 15.3), Anaplasma platys (6.5%; 95% CI: 4.5, 8.9), Babesia vogeli (5.5%, 95% CI: 3.7, 7.8) and Babesia gibsoni (0.2%, 95% CI: 0.01, 1.06). Concurrent infection with more than one TBD pathogen occurred in 39% of cases. Potential tick vectors, Rhipicephalus (most commonly) and/or Haemaphysalis ticks were found on 278 (53%) of dogs examined.

Conclusions

At least 6 species of canine tick-borne pathogens are present in India. Hepatozoon canis was the most common pathogen and ticks belonging to the genus Rhipicephalus were encountered most frequently. Polymerase chain reaction was more sensitive in detecting circulating pathogens compared with peripheral blood smear examination. As co-infections with canine TBD pathogens were common, Indian veterinary practitioners should be cognisant that the discovery of one such pathogen raises the potential for multiple infections which may warrant different clinical management strategies.

Canine and feline cardiopulmonary parasitic nematodes in Europe: emerging and underestimated

Cardiopulmonary nematodes of dogs and cats cause parasitic diseases of central relevance in current veterinary practice. In the recent past the distribution of canine and feline heartworms and lungworms has increased in various geographical areas, including Europe. This is true especially for the metastrongyloids Aelurostrongylus abstrusus, Angiostrongylus vasorum and Crenosoma vulpis, the filarioid Dirofilaria immitis and the trichuroid Eucoleus aerophilus (syn. Capillaria aerophila). The reasons of this emergence are little known but many drivers such as global warming, changes in vector epidemiology and movements in animal populations, may be taken into account. The purpose of this article is to review the knowledge of the most important heartworm and lungworm infections of dogs and cats in Europe. In particular recent advances in epidemiology, clinical and control are described and discussed.