Introduction

Mixed parasitic infections are frequently observed in dogs, carrying significant clinical and zoonotic implications (Tran Nguyen-Ho- et al. 2023, Macedo et al. 2022). Dogs can harbor a variety of ectoparasites, such as fleas (Ctenocephalides canis, Pulex irritans), ticks (Rhipicephalus sanguineus, Amblyomma americanum), and mites (Demodex canis, Sarcoptes scabiei), as well as endoparasites like roundworms (Toxocara canis, Ancylostoma caninum) and tapeworms (Dipylidium caninum) (Ortega-Pacheco and Jimenez-Coello 2025). These parasites not only inflict direct harm upon the host, leading to conditions such as pruritus, reduced body condition score, and enteric signs, but also serve as vectors for various pathogens, thereby posing a public health risk (Alba-Hurtado et al. 2022, Despommier and Toxocariasis 2003). For instance, Rhipicephalus sanguineus is known to transmit several zoonotic microorganisms (Do et al. 2024, Ghodrati et al. 2024), and Toxocara canis is a well-recognized cause of toxocariasis in humans (Yang et al. 2025, Reginaldo et al. 2025). The impact of co-infection interactions on parasite transmission dynamics can vary with spatial scale (Keegan et al. 2024).

Previous studies have reported considerable prevalence of canine ectoparasites and endoparasites in South Asia. In Bangladesh, studies have shown ectoparasite infestation rates ranging from 59.57% to 64% in dogs, with Ctenocephalides canis and Rhipicephalus sanguineus being predominant species (Zineldar et al. 2023, Sadia Authoy et al. 2023). Concurrently, gastrointestinal parasitic infections are highly prevalent, with recent studies in Dhaka reporting an overall prevalence of 63.33% in dogs, where Toxocara canis is frequently identified (Bayazid et al. 2025). Although mixed parasitic infections in dogs have been reported globally, published reports describing concurrent infection with Ctenocephalides canis, Rhipicephalus sanguineus, and Toxocara canis in a single host remain scarce. To the best of our knowledge, this is one of the few documented reports of such a specific triple co-infection from Bangladesh, highlighting the potential for simultaneous ecto- and endoparasitic infestations in companion animals within the region. This case report details this triple parasitic co-infection in a domestic dog, emphasizing the diagnostic approach, treatment, and broader implications for animal and human health.

Case history

A 2-year-old male local breed dog presented with severe pruritus, reduced body condition score, and enteric signs. The owner reported a history of persistent pruritus and visible ectoparasites. Further details regarding the dog’s environment, vaccination status, and previous deworming history were collected to establish a comprehensive case profile.

Diagnosis

Fleas and ticks were manually removed from the dog’s body using fine-tipped forceps. Fleas were collected mainly from the dorsal trunk and inguinal regions, whereas ticks were collected from the ears and neck. Adult Toxocara canis worms were recovered from freshly voided feces after spontaneous passage. Each parasite specimen was preserved separately in sterile containers containing 70% ethanol and transported to the laboratory. Before microscopic examination, specimens were rinsed with normal saline, examined grossly, and subsequently evaluated under a stereomicroscope (Olympus SZ61, Olympus Corporation, Tokyo, Japan) for detailed morphological identification.

Gross examination revealed multiple attached ectoparasites and localized dermatological lesions in the ventral abdominal region (Supplementary Figure S1). Diagnosis was established through gross and microscopic examinations of parasites collected from the patient. The identification of each parasite species was performed using the standard morphological taxonomic keys described in Helminths, Arthropods and Protozoa of Domesticated Animals, Georgis’ Parasitology for Veterinarians and Ticks of Domestic Animals in Africa: A Guide to Identification of Species (Walker Alan 2003, Bowman and Georgi 2021, ’Soulsby and Helminths 1982). Diagnostic identification was based on established morphological characteristics observed under a stereomicroscope (Olympus SZ61, Olympus Corporation, Tokyo, Japan) and independently verified by a veterinary parasitologist from the Department of Parasitology, Bangladesh Agricultural University (Table 1).

Table 1 Comparative morphological characteristics for the identification of Toxocara canis, Ctenocephalides canis, and Rhipicephalus sanguineus
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These morphological characteristics (Figs. 1 and 2), particularly the hexagonal basis capituli of R. sanguineus, the specific comb structure of C. canis, and the cervical alae of T. canis, provided definitive evidence for the triple parasitic co-infection and were consistent with previously published taxonomic descriptions (Walker Alan 2003, Bowman and Georgi 2021, ’Soulsby and Helminths 1982). Approximately 35 adult Ctenocephalides canis, 12 adult Rhipicephalus sanguineus and 4 adult Toxocara canis specimens were recovered from the affected dog.

Fig. 1
Fig. 1
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Gross morphological features of Toxocara canis (A), Ctenocephalides canis (B), and Rhipicephalus sanguineus (C) specimens recovered from a domestic dog

Fig. 2
Fig. 2
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This figure provides detailed microscopic views of the parasitic species, crucial for definitive identification. Panel (A) shows the anterior end of Toxocara canis. Panel (B) displays microscopic features of Ctenocephalides canis. Panel (C) illustrates the anterior and Panel (D) the posterior parts of Rhipicephalus sanguineus

Treatment and follow-up of the case and control measures

The patient received a comprehensive antiparasitic regimen designed to simultaneously address both ecto and endoparasitic burdens. Following standard veterinary protocols (Simparica ), the dog was administered a combination product containing sarolaner (1200 µg/kg), moxidectin (24 µg/kg), and pyrantel pamoate (5000 µg/kg) in a single oral dose.

Treatment guidelines and supportive therapy

Antiparasitic administration

The oral tablet was administered with food to ensure optimal absorption. Sarolaner was selected because of its proven efficacy against fleas and ticks, while moxidectin and pyrantel pamoate provide broad-spectrum activity against gastrointestinal nematodes including T. canis (Simparica ). The combination allows simultaneous treatment of ectoparasitic and endoparasitic infections with a single administration. This provides immediate and persistent efficacy against fleas and ticks for one month, concurrently treating the T. canis infection.

Supportive care

To manage severe pruritus and skin irritation, a topical soothing shampoo and a short course of antihistamines were administered. Enteric signs were managed with a highly digestible diet and probiotic supplementation for seven days.

Environmental control

The owner was instructed to thoroughly clean the dog’s living environment and apply a permethrin-based environmental insecticide to eliminate flea larvae, pupae, adult fleas, and off-host tick stages. Environmental treatment is recommended because most stages of the flea life cycle occur away from the host, and environmental decontamination significantly reduces reinfestation and improves long-term parasite control (ESCCAP, Dryden 2009).

Follow-up and recovery

Clinical improvement was observed within 48 h, marked by a significant reduction in pruritus and improved appetite. A follow-up examination at 14 days revealed no visible ectoparasites and a negative fecal flotation test for T. canis eggs. The animal showed complete recovery by the end of the 30-day follow-up period.

Discussion

While mixed infections are frequently suspected in clinical practice, this case offers detailed morphological documentation of a specific triple co-infection, underscoring the necessity for broad-spectrum parasiticides in regions where environmental conditions and stray animal populations favor high parasite diversity. The co-occurrence of Ctenocephalides canis, Rhipicephalus sanguineus, and Toxocara canis underscores the need for comprehensive diagnostic approaches that consider both ecto- and endoparasites. The zoonotic potential of these parasites, particularly R. sanguineus as a vector for various pathogens (Do et al. 2024, Ghodrati et al. 2024, Özübek 2024, Gharbi et al. 2024) and T. canis as a cause of human toxocariasis (Yang et al. 2025, Reginaldo et al. 2025), emphasizes the public health significance of such cases. It is important to note that human exposure risk was not directly assessed through household surveys or diagnostic testing in this study. The zoonotic implications discussed in this report are based on the established zoonotic potential of T. canis and pathogen transmission associated with R. sanguineus as reported in the literature (Alba-Hurtado et al. 2022, Do et al. 2024, Keegan et al. 2024). Furthermore, although no recurrence was observed during the 30-day follow-up period, longer monitoring may be necessary to exclude the possibility of reinfection or delayed relapse, particularly in environments with persistent parasite contamination.

Molecular confirmation of parasite identity through PCR amplification and DNA sequencing was not performed because molecular diagnostic facilities and research funding were unavailable during this case investigation. Nevertheless, morphological identification was considered reliable because all recovered specimens exhibited the characteristic diagnostic features described in internationally accepted taxonomic keys (Bowman and Georgi 2021). Future studies should incorporate molecular techniques to further validate species identification and investigate parasite genetic diversity.

Effective control strategies must therefore encompass both animal treatment and environmental management, aligning with the ‘One Health’ perspective (Giannelli et al. 2024). Studies have shown the epidemiological characteristics of ectoparasite infestation in domestic dogs (Tran Nguyen-Ho- et al. 2023, Zineldar et al. 2023, Sadia Authoy et al. 2023) and the prevalence of potentially zoonotic endoparasites (Reginaldo et al. 2025, Bayazid et al. 2025). These findings are consistent with previous reports from Bangladesh, where Ctenocephalides canis and Rhipicephalus sanguineus have been identified as the predominant ectoparasites of domestic dogs (Sadia Authoy et al. 2023), while Toxocara canis remains one of the most frequently detected zoonotic gastrointestinal nematodes (Bayazid et al. 2025). The present report extends these observations by documenting the concurrent occurrence of all three parasite species in a single dog. The impact of co-infection interactions on between-host parasite transmission dynamics also represents a critical area of research (Keegan et al. 2024, Hananeh et al. 2022, Milićević et al. 2025). Future investigations should employ polymerase chain reaction (PCR) assays followed by sequencing of mitochondrial cytochrome-c oxidase subunit I (cox1), 16 S rRNA and Internal Transcribed Spacer (ITS) gene regions to confirm parasite identity, evaluate genetic diversity, detect cryptic species and identify associated vector-borne pathogens that may not be distinguishable through morphology alone (Nyema et al. 2024, Zazueta-Islas et al. 2024).

From a One Health perspective, routine deworming of dogs, year-round flea and tick control, responsible pet ownership, proper disposal of animal feces, public education regarding zoonotic parasites and coordinated surveillance involving veterinarians and public health authorities are recommended to reduce transmission risks at the community level.

Conclusions

This case report documents a significant instance of triple parasitic co-infection involving Ctenocephalides canis, Rhipicephalus sanguineus, and Toxocara canis in a domestic dog. The successful management of this case through integrated diagnostic and therapeutic protocols highlights the critical need for vigilance in veterinary practice. Crucially, this case emphasizes the profound zoonotic importance of these parasites. Toxocara canis poses a direct threat to human health through visceral and ocular larva migrans, while Rhipicephalus sanguineus serves as a primary vector for life-threatening zoonotic diseases such as Rocky Mountain spotted fever and ehrlichiosis. Therefore, routine parasitic screening and the implementation of year-round preventive measures are not merely animal health concerns but constitute essential public health interventions. A collaborative ‘One Health’ approach involving pet owners, veterinarians, and public health officials is vital to mitigate the risks of zoonotic transmission in urban and rural environments.