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Abanico veterinario

On-line version ISSN 2448-6132Print version ISSN 2007-428X

Abanico vet vol.9  Tepic  2019 

Original Article

Prevalence of Dirofilaria immitis in domestic canines from two municipalities in the tropic of Guerrero, Mexico

1School of Veterinary Medicine and Zootechnics No. 3, Autonomous University of Guerrero, Tecpan de Galeana, Guerrero, Mexico.

2Pub-Graduação em Ciência Animal Program, School of Agricultural Sciences and Veterinary Medicine - Pontifícia Universidade Católica do Paraná, São José dos Pinhais, Brazil.


The objective of the present study was to determine the prevalence of Dirofilaria immitis (DI) in domestic canines in the municipalities of Cuautepec and Acapulco de Juárez, Guerrero, Mexico. Cluster sampling was used according to the selected addresses. Blood samples were obtained only from dogs older than one year of the two municipalities. In the study, 15.68 % were found in the municipality of Cuautepec and 7.44% in domestic canines positive for microfilariae in Acapulco de Juárez. The highest percentage of positive animals was found in males, in animals> 3 years of age and small and medium animals in Cuautepec municipality (P <0.05). Likewise, in the municipality of Acapulco de Juárez, a higher percentage of positive females was found, with an age> 3 years of age, of an indefinite mestizo race and living outside the home (P <0.05). It is concluded that domestic canines in the municipalities of Cuautepec and Acapulco de Juárez, Guerrero, found a high prevalence of DI, and males had a higher percentage in the municipality of Cuautepec and females in Acapulco de Juárez.

Keywords: Gastrointestinal nematodes; infestation; right heart; Dirofilaria immitis; sex; bood samples


Canine filariasis is the disease that gives name to the infestation by the parasite Dirofilaria in dogs, also known as heartworm, cardiac verminosis, heartworm disease, worm disease in the heart (Rawlings and Calvert, 1997, Montoya-Alonso et al., 2011; Alho et al., 2018). In the world there are two species of Dirofilaria, of interest for human and veterinary medicine (D. repens and D. immitis) (Liotta et al., 2013). D. repens is a disease present in Europe, Africa and Asia; on the other hand DI or heartworm present in mammals, mainly carnivores and primates: dogs, cats, foxes, coyotes, ferrets and sea lions (Vezzani et al., 2006, Orihel et al., 1998, Genchi et al., 2011; Alho et al., 2018).

DI is a cosmopolitan nematode, originally considered of strict veterinary importance; subsequently it was recognized as zoonotic; in humans it causes skin and lung lesions. Cases of dirofilariasis have been reported in large mesenteric vessels, peritoneal vessels, spermatic cord and "right" heart (Chinapa et al., 2004, Sánchez-Klinge et al., 2011, Wang et al., 2019).

Clinically ill animals show few signs of infestation; although these depend on the severity of the disease, the location of the filaria, the time that has been present (Knight, 1980, Ceribasi and Simsek, 2012, Dearsley et al., 2019), and the amount of damage to the heart; as well as the lungs, liver and other organs; but always the affected animal will show less tolerance to exercise (Fox et al., 1999, Ceribasi and Simsek, 2012, Wang et al., 2019). The adult worms, in the canine, form a mass in the right ventricle causing a congestive heart failure in the pulmonary artery; while microfilariae circulate in the blood (Knight, 1980, Fox et al., 1999, Montoya-Alonso et al., 2011, Alho et al., 2018).

Microfilaria circulates in the bloodstream, but cannot develop adult worms without passing through an intermediate and transmitting host, the "hematophagous" mosquito that belong to the Phylum Arthropoda, Insecta Class, Diptera Order, Nematocera Suborder, Culicidae Family (Christensen, 1978; Liotta et al., 2013; Alho et al., 2018) and the genera: Aedes, Anopheles, Culex and Taeniohynchus; the family has 3,000 species included in 34 genera, receptive as intermediate hosts and biological DI vectors (Sánchez-Klinge et al., 2011, Urquhart et al., 2001, Simón et al., 2012, Dearsley et al., 2019) .

For the biological cycle to occur in the mosquito, it is necessary that in the infected mosquito a series of transformations take place in larval stages (L1, L2 and L3), all this happens between 13 to 16 days (Kittleson and Kienle, 2000; Bowman and Lynn, 1999; Montoya-Alonso et al., 2011; Dearsley et al., 2019). On the other hand, the development in the host mammal occurs after 2 days to 3 months, reaching lengths of 3.2 to 11 cm (L4 and 5; Bowman and Lynn, 1999; Liotta et al., 2013; Wang et al., 2019). The number of adult worms harbored varies from 1 to more than 250 in the dog (Dillon, 2000; Dearsley et al., 2019). The survival of DI in the dog is from 3 to 8 years (Atkins, 1994, Dillon, 2000, Newton, 1968, Liotta et al., 2013, Dearsley et al., 2019).

In Mexico epidemiological studies have been conducted to determine the presence of DI in dogs, and its prevalence varies according to the living conditions of the animals and the climatic variations of the region (Bautista-Garfias et al., 2001). Indeed, the highest prevalences are found in tropical and subtropical regions (Labarthe and Guerrero, 2005, Liotta et al., 2013, Wang et al., 2019). In a prevalence study conducted in the 11 municipalities of Nayarit state, they found a prevalence range of 2.5 to 33.33 % (González-Morteo et al., 2015, Wang et al., 2019). Rodríguez-Vivas et al. (1994), conducted a study in Mérida city, Yucatán, and found a prevalence of 12.5 %.

The blood test is the most practical and simple method for the diagnosis of DI; although it is a qualitative test, it does not indicate the number of microfilariae and the severity of the lesions. In fact, the diagnosis is usually established from regular blood tests (Paras, 2011, Wang et al., 2019), such as blood count, cases of chronic cough in individuals living in endemic areas and to detect worms adults in the heart through radiographic plates, especially in cases of vena cava syndrome (García et al., 2011; Alho et al., 2018). In sick animals, a clinical diagnosis is made by several methods for the identification of microfilariae of infected dogs: a) method of direct observation of serum, b) serum concentration method; c) immunological methods to detect antigens and d) modified Knott technique (Ferrer -Montaño et al., 2002; Fernández et al., 2017; Dearsley et al., 2019).

In Guerrero state and particularly in the municipalities of Acapulco de Juárez and Cuautepec, there is no information on the prevalence of DI in domestic canines. Therefore, the objective of the present study was to determine the prevalence of Dirofilaria immitis in domestic canines in the municipalities of Cuautepec and Acapulco de Juárez, Guerrero, Mexico.


Study area

The present epidemiological study was conducted in the municipalities of Cuautepec and Acapulco de Juárez, Guerrero, Mexico. This region of the state belongs to the tropics and is located between the coordinates 16 ° 51'48 "of Latitude North and 99 ° 53'24" of West Longitude, with an altitude of between 0 and 2,000 m a.s.l. The highest average temperature and humidity (39.5 °C and 76 %) occur during the summer months and the lowest months (16 °C and <70 %) during the winter months (García, 1974).


196 domestic dogs were randomly sampled, 102 in the municipality of Cuautepec (41 males and 61 females) and 94 Acapulco de Juárez (41 males and 53 females). In both municipalities, the sampling criterion for animals was from north to south and from east to west, taking as a reference the center of each municipality. Of the animals found by domiciled visits, only those older than one year were sampled, because the biological cycle of the parasite is long and for the diagnostic method used it is required to have microfilariae in its plasma, about 7 months after the infestation (González -Morteo et al., 2015). All the procedures of sampling and management of the animals reported in the present work were according to the Official Mexican Standard with technical specifications of the production, use and care of laboratory animals (SAGARPA, 2001).

Collection and preparation of samples

The blood samples were taken in the hours between 18:00 - 20:00 h, by the nocturnal periodicity. Prior to the extraction of blood, the animal was subjected to depilating the area; with the respective antisepsis, 3 ml of blood with anticoagulant (EDTA) were extracted from the cephalic vein and the samples were kept at 4 to 6 °C for 4 days for further analysis.

Subsequently, blood smears were performed in order to identify dead dirofilaria larvae. For the Thick Drop technique, a drop of fresh blood was placed on a slide, extending it to cover a double surface of the original; finally, the preparation was allowed to dry (in the air or in an oven at 37 °C) and traces of larval motility were observed under the microscope. The modified Knott technique was performed by mixing 1 ml of blood with 9 ml of 2 % formaldehyde in a glass tube; the mixture was centrifuged for 8 minutes at 1500 r.p.m .; the supernatant was removed, and the 0.1 % methylene blue pellet was added, and the pellet was then examined under a microscope.

Variables of study

Sex, age (1, 3 and> 3 years), height (girl, medium, large), race (pure, mestizo undefined), body condition (CC, scale: 1 to 5) (Laflamme, 1997), activity or work in the field, cattle herding, care of the home, location (north, south, east or west) and possible risk factors such as the degree of urbanization of the colony-housing where the dogs lived and exposure to mosquitoes.

Statistical analysis

The sampling system by municipality Cuautepec and Acapulco de Juárez, was by conglomerates according to the location of the households sampled (dynamics: north to south and east to west). Contingency tests were carried out in 2x2 tables; the proportions between variables were analyzed with the Chi-square test to establish the correlation between sex and disease. All the results were analyzed with the statistical program SAS (2004).


In the municipality of Cuautepec, 15.68 % of positive canines were found in microfilariae. The highest percentage of positive animals was found in males than in females and animals> 3 years of age (P <0.05). The canines that presented the highest percentage were those of CC of 4 and 5 that the minors on this scale. On the other hand, a higher percentage of positive animals was found in small and medium size canines (P <0.05). A higher percentage was also found in canines of an indefinite mestizo breed, who lived outside the home, in coexistence with other congeners and who spent more time caring for the home (P <0.05) (Table 1).

The results of the present study show that a high prevalence of ID in canines was found in Cuautepec municipality. Results consistent with this study were similar to those found in the municipalities of Bahía de Banderas Nayarit (12.7 % prevalence) (González-Morteo et al., 2015) and Chontalpa Tabasco (17.5 % prevalence) (Torres-Chable et al., 2018); but different from those reported by Rodríguez-Vivas et al. (1994) in Yucatán state (6.54 % prevalence). These same investigations (Rodríguez-Vivas et al., 1994, González-Morteo et al., 2015, Torres-Chable et al., 2018), mention not having found an effect between the sexes (males and females), age, height, race, place where they lived (inside or outside the house) and coexistence with other dogs.

However, in the present study the animals where the microfilaria were found were males, with high CC (3 and 5 points), small size and medium size. This can be explained as follows: working dogs are generally of an indefinite mestizo breed, medium size, they inhabit outside the home, they have the possibility of interacting more with other dogs and due to the location they are more exposed to mosquito bites host of the DI parasite.

Table 1 Frequency and percentage of positive canines to DI microfilaria in the municipality of Cuautepec. 

Variable Category Samples (n) Positive to microfilaria (Knott)
Frequency %
Sex Female 41 3a 7b
Male 61 13b 21a
Age (years) 1 36 4a 11b
3 38 7a 18a
>3 28 5a 18a
1CC 1 a 2 24 1a 4c
3 49 8b 16b
4 a 5 29 7b 24a
Size Little 22 3a 14b
Medium 77 13b 17b
Large 3 0a 0a
Race Pure 31 2a 6b
Mestizo 71 14b 20a
Living place Interior 16 0a 0b
Exterior 86 16b 19a
Co-existence Farm 49 2a 4b
Canines 53 14b 26a
Activity Home 38 1a 4b
Field 64 5b 23a
Location Norte 26 3a 18c
South 22 7b 19c
East 17 9b 24b
West 37 7b 11a
Microfilaria Negative 86 0a 0%a
Positive 16 16b 15.65%b

1Body condition (CC, scale 1 to 5).

a,b,c The literals inside column show significant difference between % (P<0.05).

On the other hand, in the municipality of Acapulco de Juárez, 7.44 % of domestic dogs positive for microfilaria were found. The highest percentage of positive animals was found in small animals, with CC from 1 to 3 and living with congeners in the home (P <0.05). Likewise, a higher percentage of positive females was found, with an age> 3 years of age, of an indefinite mestizo race and living outside the home (P <0.05, Table 2).

The results of the present study show that, in the city of Acapulco de Juárez, Guerrero, a low prevalence of DI was found in domestic dogs. Results similar to those of this study were reported by Rodríguez-Vivas et al. (1994) in the state of Yucatán (6.54% prevalence). Contrary to these results, they were different from those found in the municipality of San Blas Nayarit by González-Morteo et al. (2015; 33.33% prevalence) and by Torres-Chable et al. (2018) in Chontalpa Tabasco (17.5% prevalence). These same investigations (Rodríguez-Vivas et al., 1994, González-Morteo et al., 2015, Torres-Chable et al., 2018), mention not having found an effect between the sexes (males and females), age, height, race, place where they lived (inside or outside the house) and coexistence with other dogs.

However, in the present study the animals where the microfilaria were found were male, of low CC (1 to 3 points), small size and medium size; this can be explained as follows: most pets are of medium size, live outside the home, have the possibility of interacting more with other dogs and have a greater exposure to mosquito bites intermediate host of the parasite.

In the present study it can be mentioned that at least in the sampled municipalities, DI disease prevails; due to this and by some particular characteristics to consider it as an enzootia to the disease (Dirofilariasis). As the authors mentioned in their localities have considered it; It is possible to use this term because in this specific geographical area of the state of Guerrero the dog populations that live outside the home are continuously affected by mosquitoes and consequently by DI.

Table 2 Frequency and percentage of positive canines to DI microfilaria in Acapulco city. 

Variable Category n Positive to microfilariae (Knott)
Frequency %
Sex Female 53 6a 11%a
Male 41 1b 2%b
Age (months) 8 a 12 40 3a 8%a
13 a 36 36 2a 6%a
>37 19 2a 11%b
CC scale 1 a 3 50 6a 12%a
3 a 5 44 1b 2%b
Size small 36 6a 17%a
Medium 42 0b 0%b
large 16 1b 6%b
Race Defined 21 0a 0%a
Indefinite mestiza 73 7b 10%b
Habitat Interior 12 0a 0%a
Exterior 82 7b 9%b
Living with animals No 34 0a 0%a
Dogs 60 7b 12%b
Microfilaria Negative 87 0a 0%a
Positive 7 7b 7.44%b

a,bThe literals inside column show significant difference between frequency and percentage (P<0.05)


The results of the present study allow us to conclude that, in the domestic dogs of the municipalities of Cuautepec and Acapulco de Juárez, Guerrero, a high prevalence of DI was found (average: 11.56 %), and the males had a higher percentage of infestation (21 %; Cuautepec). Likewise, it was found that canines of medium size and those with high CC were positive in the parasite detection tests.


The data presented in this manuscript were part of the thesis of José Carlos Cisneros. We thank Dr. Abner Gutiérrez, from the Department of Agronomy Division of Life Sciences, Campus Irapuato - Salamanca, University of Guanajuato, for all the facilities in the analysis of the samples. We thank all members of the research group "Animal Production Systems" of the School of Veterinary Medicine and Zootechnics No. 3, Autonomous University of Guerrero


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Received: February 21, 2019; Accepted: July 10, 2019

*Responsible author: Perla Irasema Romero-Rodríguez.

**Corresponding author: José Luis Ponce-Covarrubias. Carr. Acapulco-Zihuatanejo km. 106 + 9000 Col. Las Tunas, C.P. 40900. Guerrero, Mexico. E-mail:

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