Babesiosis is a disease caused by species of Apicomplexan protozoa of the genus Babesia. Species of Babesia parasitize the red blood cells of mammals and may cause clinical disease with varying levels of morbidity or mortality. Babesia spp. are naturally maintained and transmitted in hosts through their respective hard tick vectors, and a range of domestic and wild mammals serve as reservoirs for these parasites. Humans may become accidentally infected by some species of Babesia through bites from infected ticks or through blood transfusions and organ transplants from infected donors. Depending on the immune status of the host, humans can either remain asymptomatic (thus acting as carrier hosts) or suffer from clinical disease with varying intensities. Several known species and unknown or novel species of Babesia are being reported to be associated with zoonotic infection and disease. This Chapter discusses the transmission, pathogenesis, epidemiology, treatment and control of zoonotic babesiosis.

Filariases are neglected tropical diseases caused by Clade III parasitic nematodes transmitted by biting insects as microfilaria which mature into female and male adults in the host. One example of filariasis is lymphatic filariasis or elephantiasis, caused by three species of filaria: Brugia malayi, Wuchereria bancrofti, and/or Brugia timori. Elephantiasis results from the occlusion of lymphatic vessels by adult parasites and subsequent swelling of the limbs. It is a disfiguring disease that occurs in 120 million people worldwide. Another filarial disease is onchocerciasis caused by Onchocerca volvulus. Microfilaria of this parasite invade the eye producing corneal scarring and blindness. The infected female blackflies that transmit these microfilaria belong to the Simulium genus, and breed in fast flowing rivers. Onchocerciasis occurs near these rivers and gives rise to the common name of the disease, i.e., "river blindness." Diethylcarbamazine (Hetrazan[R]) was described as effective for treating filariases over 75 years ago by Yellapragada Subbarow and collaborators and is currently still in use. Diethylcarbamazine is characterized by a simple but flexible structure that provides it with the ability to combine with several target proteins, and a complex mode of action with effects on both filarial parasites and hosts. This Chapter reviews new observations on the activation of Transient Receptor Potential (TRP) ion-channels of B. malayi and older observations on the mechanisms of action of diethylcarbamazine. Diethylcarbamazine has three major effects: 1) A direct activating effect on filaria TRP channels producing transient inhibition of motility; 2) Reduction of host and parasite PGI2 and PGE2 production, thereby reducing host immune suppression; and 3) Activation and adhesion of host granulocytes which attack the filaria. We emphasize recent observations that include activation of TRP channels by diethylcarbamazine, an underappreciated mode of action of this classic anthelmintic.

Cystic echinococcosis (CE) remains one of the most persistent neglected zoonoses despite profound knowledge of the life cycle of Echinococcus granulosus sensu lato and the availability of well-established control tools. Persistence of CE is driven by interacting barriers, i.e., rapid reinfection of dogs, continued access of dogs to infected offal and carcasses, informal slaughter, suboptimal surveillance feedback, fragmented institutional responsibility, and misaligned economic incentives. These constraints are especially evident in sheep-farming and agro-pastoral systems, where dogs, livestock, household practices, and rural economies remain closely connected. Effective control requires a One Health approach that combines repeated praziquantel treatment of dogs, safe management of offal and carcasses, inspected slaughter, livestock surveillance, community engagement, and management of owned, semi-owned, and free-roaming dogs. This Chapter examines the underlying factors that challenge eradication of CE from many endemic settings. Particular attention is given to prevention, health education, and edutainment, since CE control primarily depends on achieving change in a small number of high-risk practices that are often normalized in daily pastoral life. Sardinia and comparable Mediterranean settings are used to illustrate how persistent sheep infection, fertile cysts, working-dog ecology, informal slaughter, incomplete dog prophylaxis, and governance gaps sustain endemic transmission even where the disease is well recognized. The Chapter argues that CE persistence reflects failures of continuity, traceability, and field delivery; durable control therefore depends on the organization of dog management, slaughter systems, surveillance, and community action as much as on parasitology.

Sarcocystosis is an emerging zoonotic disease caused by apicomplexan parasites of the genus Sarcocystis, which can infect a wide range of hosts, including humans, animals, reptiles, and birds. Humans may serve as either definitive or intermediate hosts, depending on Sarcocystis species. Consumption of undercooked beef containing mature sarcocysts of Sarcocystis hominis or Sarcocystis heydorni, or of raw or partially cooked pork containing Sarcocystis suihominis zoitocysts, may lead to intestinal sarcocystosis in humans. In contrast, muscular sarcocystosis follows ingestion of food or water contaminated with zoonotic Sarcocystis spp. sporocysts, as evidenced by infection outbreaks by Sarcocystis nesbitti among travelers returning from exotic destinations in Malaysia. Further, Sarcocystis fayeri, which cycles between horses and dogs, has been implicated in cases of food poisoning in humans following consumption of raw horse meat. Clinical features range from asymptomatic cases to acute symptoms, such as muscle pain, fever, and, in severe cases, neurological complications. Diagnosis relies on clinical presentation supported by microscopy, histopathology, serology, and advanced molecular techniques. Therapeutic options are limited; antiprotozoal agents including sulfadiazine, pyrimethamine, decoquinate, clindamycin, and triazine derivatives have shown high efficacies. Preventive measures focus on hygienic meat handling, thorough cooking, and restricting carrion scavenging by stray carnivores. Increasing human-wildlife interactions elevate the risk of cross-species transmission of novel Sarcocystis species. Adopting a One Health approach is fundamental for understanding the epidemiology and transmission dynamics of zoonotic sarcocystosis and reducing future outbreaks through effective diagnostics, therapeutics, and preventive interventions.

Soil-transmitted helminths (STHs) are intestinal parasitic worms that present a significant global health challenge. Traditionally, the diagnosis of STH infections has relied on microscopy; however, molecular tests such as quantitative PCR (qPCR) are now widely adopted for their greater sensitivity, increasingly reduced cost and higher throughput. Recent evidence highlights genetic diversity in both coding and non-coding DNA regions of STHs routinely targeted by molecular diagnostics. Most qPCR assays have been developed using a limited selection of parasite isolates, thus likely overlooking the substantial genetic variation present within and among STH populations worldwide. Such genetic diversity can significantly impact the diagnostic targets of molecular tests, potentially reducing their sensitivity and leading to false-negative results. Therefore, there is growing recognition of the need to develop diagnostic tools that account for this genetic variation. In this Chapter, we outline current advances in STH genomics and review recent work on the assessment of genetic diversity directly from fecal samples, especially as access to adult worms becomes increasingly difficult. These studies emphasize the importance of thoroughly evaluating current and future diagnostic methods prior to their implementation to effectively guide control measures and policy decisions regarding the cessation of STH deworming. Together, these findings lay the groundwork for genomic epidemiology and the sustainable control of STHs as a public health issue.

Cyathostomins (also known as small strongyles or small redworms) are ubiquitous parasites of equids. They are found in a wide range of climatic regions, and inhabit the large intestine of their hosts. While infections are often sub-clinical, clinical consequences ranging from chronic to acute, and most notably, acute larval cyathostominosis, can occur in specific circumstances. Control of cyathostomin infection is complicated by widespread drug resistance. This Chapter provides a broad review of cyathostomin biology and host-parasite relationships, and also highlights significant knowledge gaps, for example relating to immune response, and the community dynamics of mixed populations of cyathostomins within the host, that complicate the development of sustainable parasite control strategies.

Carnivorous wild mammals often harbor a high diversity and high prevalence of parasites, many of which possess zoonotic potential or are of relevance for domestic animal health. In this Chapter, we summarize studies on endoparasites of the most common wild canids (red and arctic foxes, golden jackals, coyotes, grey wolves and raccoon dogs), felids (lynxes and European wildcats) and bears (brown and black bears) in the Palearctic and Nearctic regions since the turn of the millennium. Overall, the red fox stands out as the best-studied species, with the highest endoparasite diversity reported, and high detection rates of zoonotic parasites or parasites of significance to domestic animal health. The red fox synurbic lifestyle further underscores its relevance as a source of potential pathogen spillover. The epidemiological role of grey wolves, golden jackals, coyotes and raccoon dogs requires further investigation given their geographical expansion. Wild felids represent a potentially important reservoir for parasites that are pathogenic to domestic cats, while bears are reported to play a minor role for the circulation of zoonotic and domestic animal parasites. Identified knowledge gaps include a lack of studies from Asia and North America in comparison to Europe, and of studies on felids and bears as compared to canids.

Zoonotic parasite spillover is a multi-host process shaped by interactions among wildlife, domestic animals, vector or intermediate hosts, humans, and the environment. Transmission is governed by complex parasite life cycles involving intermediate and bridge hosts and environmental stages, all of which regulate development, persistence, and exposure. Spillover occurs when host-parasite compatibility, ecological overlap, and human behaviors converge to enable cross-species transmission. Anthropogenic changes, including deforestation, urbanization, agricultural intensification, pollution, and climate change, are increasing ecosystem permeability, altering host immunity, and intensifying contact among species, thereby elevating spillover risk. Establishment in humans depends on the ability of parasites to overcome molecular and physiological barriers and, in some cases, sustain onward transmission. Although many zoonotic parasites establish dead-end infections, they may still impose significant morbidity. This Chapter revisits key concepts, including reservoirs, intermediate and bridge hosts, and the processes of shedding, spillover, and spread, integrating ecological and evolutionary mechanisms such as host-switching and parasite adaptation. We further examine how environmental change reshapes transmission pathways and host interactions and discuss key examples of parasite zoonotic spillover. Finally, we propose a One Health framework that incorporates life cycles, environmental processes, and multi-host networks, offering a more realistic foundation to understand, anticipate, and prevent zoonotic parasite emergence in a rapidly changing world.

Control of malaria uses a variety of tools including drugs, vaccines, and insecticidal strategies to reduce parasite transmission by mosquito vectors. A new tool that eliminates parasites in mosquitoes by delivering antimalarials to the insects rather than infected people is emerging as a simple, relatively inexpensive malaria control strategy. In this Chapter, we review antimalarials that show efficacy in mosquitoes, effective methods to deliver compounds into the insects, and strategies to optimize this new tool as a useful component of the arsenal of strategies to combat malaria.

Entamoeba is a genus of anaerobic protists that infect humans and a wide range of animal hosts worldwide, and that are also detected in environmental reservoirs. Of particular importance is Entamoeba histolytica, the causative agent of amoebiasis, which accounts for more than 55,000 deaths each year and remains a major public health concern. Given this substantial burden, and the fact that pathogenic and non-pathogenic species of Entamoeba cannot be distinguished based on morphology alone, molecular approaches have become essential for accurate diagnosis, taxonomy, and epidemiological surveillance. In this Chapter, we systematically review the impact of DNA sequencing technologies on Entamoeba research from 1987 to 2025. A bibliographic search was conducted using PubMed and Google Scholar, combining the names of all recognized Entamoeba species with keywords related to sequencing technologies, spanning from first- to fourth-generation platforms. Original research articles employing DNA sequencing for molecular identification, phylogenetic analyses, and genomic investigations were included. The literature illustrates a clear transition from morphology-based classification to Sanger sequencing of the small subunit of the ribosomal RNA (SSU rRNA) gene, which established the molecular taxonomic framework of the genus and enabled the recognition of numerous new species and ribosomal lineages. The expansion of diversity revealed by high-throughput sequencing is also addressed, together with the contribution of long-read technologies to resolving highly AT-rich and repetitive genomes. Despite these advances, challenges remain in species delineation and marker-associated biases, highlighting the ongoing need for integrative genomic approaches in Entamoeba research.

Parasites harbor diverse microbial ecosystems that include not only bacteria but also archaea, fungi, viruses and microbial eukaryotes. These parasite-associated microbiomes, long overlooked, are now recognized as important determinants of parasite development, fitness, virulence and interactions with hosts across medical, veterinary, agricultural and ecological systems. However, current understanding of parasite-associated microbiomes remains fragmented, with most studies focusing on a narrow set of human parasites, relying heavily on bacterial surveys and rarely capturing the full multi-kingdom diversity of microbial partners. Important challenges include expanding research to encompass neglected parasite groups and their non-bacterial associates, establishing causal links between microbiome members and parasite phenotypes, and overcoming the technical barriers posed by low-biomass, host-contaminated and/or experimentally intractable systems. Progress will also depend on developing robust reference genomes and analytical tools that can resolve multi-kingdom communities and integrate parasite and symbiont biology. This chapter synthesizes current knowledge across helminths, protozoa, ectoparasites and plant-infecting parasites. We consider how microbiome manipulation may contribute to parasite control while recognizing the evolutionary and ecological complexities involved in altering host-parasite-microbiome interactions. Embracing an explicitly multi-kingdom, holobiont-focused perspective promises to illuminate fundamental aspects of parasitism. Such knowledge may contribute to new avenues for mitigating the impact of parasitic diseases on human and animal health, food security and ecosystems.

Parasitic platyhelminths (Trematoda, Monogenea, and Cestoda) are responsible for widespread disease in wild and cultured fish in both freshwater and marine environments globally, impacting both human health and the sustainability of aquaculture industries. Research into these parasites primarily aims to understand the impact of infections on host species, as well as developing management strategies to reduce or eliminate disease. -Omics-based research can assist in uncovering the biology of these parasites across a range of key areas, including understanding host-pathogen interactions, identifying novel drug and vaccine targets, and recognizing the overall diversity of parasite species. To date, the application of -omics technologies to piscivorous platyhelminths has been limited. This Chapter focuses on the current availability of -omics research in fish platyhelminths, with a primary focus on parasites with definitive fish hosts, and argues that the application of these technologies may provide unprecedented opportunities for the development of novel sustainable strategies for infection and disease management and control.

Anisakidosis is a fish-borne zoonosis characterised by mild to severe gastrointestinal (GI) symptoms and potentially linked to the onset of allergic reactions and cancer. The disease follows the ingestion of marine products infected with third-stage (L3) larvae of the genera Anisakis and Phocanema. Epidemiologically, anisakiasis is most prevalent in countries where fish consumption is high, such as Japan and the Mediterranean regions; however, the globalization of dietary habits has contributed to the expansion of its incidence worldwide. In this Chapter, we provide an overview of aspects related to the disease, from the description of the biological features of L3 and fourth-stage (L4) larvae, to the mechanisms likely responsible for allergic reactions and GI lesions. Multiple factors contribute to the allergenicity of Anisakis spp., including exposure time, GI and endo-lysosomal stability and antigenic structure. A growing body of research focuses on the parasite excretory/secretory (E/S) products, including extracellular vesicles, encompassing proteolytic enzymes, immunomodulatory molecules, and potential virulence factors. E/S products play key roles in host-parasite interactions, such as tissue invasion, immune evasion, and allergic sensitization. Both in vivo and in vitro studies (conducted in murine models of infection and human epithelial and dendritic cell cultures, respectively) have enhanced current understanding of anisakidosis pathophysiology, elucidating mechanisms of mucosal damage, cytokine production, and adaptive immune responses. These models also offer insights into chronic disease outcomes, that include formation of eosinophilic granulomas, chronic abdominal pain, and a potential correlation between anisakidosis and the occurrence of a tumorigenic microenvironment in the GI tract.

Neglected tropical diseases (NTDs) encompass 20 conditions or groups of diseases that affect almost exclusively the rural poor in low- and middle-income countries (LMIC). NTDs cause severe and chronic disabilities, from disfigurement and cognitive defects to death, and present substantial public health and socioeconomic burdens. Amongst NTDs, infections by parasitic protozoans, helminths and arthropod and non-arthropod ectoparasites, are of critical importance, with soil-transmitted helminths (STHs) representing the most widespread and prevalent NTDs globally. Whilst mass drug administration is the current strategy for control of helminth (STH and schistosomiasis) infections, treatment alone is inadequate due to the absence of lasting immunity against reinfections and the persisting concern of emerging drug resistance. The prevention and ultimate elimination of parasitic NTDs would avoid unnecessary suffering and significantly reduce poverty; hence, the potential of effective antiparasitic vaccines offers hope to billions, particularly those in sub-Saharan Africa. Given the strong links between NTDs and poverty - both regarding the demographics of the most affected communities and the socio-economic impact that these diseases exert - vaccines for these conditions are often referred to as "antipoverty vaccines". Here, a comprehensive analysis of the current state of antipoverty vaccine development is provided, with a focus on the potential for antiparasitic vaccines. This encompasses both a review of the current scientific literature and an assemblage of key stake-holder perspectives obtained through semi-structured interviews, all aimed to assess the future directives, utility and acceptability of these vaccines. The causes behind the current paucity of antipoverty vaccines are explored and global policy recommendations to assist their development and acceptance addressed. There was unanimous agreement among stakeholder interviewees on the importance and value of antipoverty vaccines, although it was felt that this sentiment does not extend to funders or policymakers from the Global North. Such findings highlight the scientific challenges in/of creating these vaccines, and how such challenges are amplified by financial constraints. The lack of funding reflects low profitability and biases against diseases largely of morbidity rather than mortality, as well as potentially the issues of poor people in poor countries and race/ethnicity. Solutions to how barriers affecting vaccine uptake on the ground can be addressed are proposed, primarily involving increased access to healthcare infrastructure, enhanced compliance through education, and involvement of local communities in all stages of development and rollout.

Leishmaniasis, caused by vector-borne Leishmania spp., continues to cause a significant burden of disease around the world. These sand fly-transmitted protozoan parasites, of which numerous species exist, are responsible for cutaneous (CL), mucocutaneous (MCL), and visceral leishmaniasis (VL) - diseases which can be debilitating or even fatal, especially in immunocompromised individuals. In many areas, dogs serve as a reservoir for Leishmania. Treatment of leishmaniasis relies on a minute arsenal of chemotherapeutic drugs that are toxic, costly, or difficult to source. Meanwhile, an effective vaccine formula remains elusive, although vaccines for the prevention of canine leishmaniasis (CanL) have been in use for decades. Treatment failure (TF) is an important concern for leishmaniasis. Incomplete cure or relapse is relatively common in cases of VL and CL. When it comes to CanL, TF or relapse is typical; host immunity and drug characteristics play a major role. Meanwhile, drug resistance (DR) has also become a major issue in some regions and may play an important role in TF. Leishmania parasites possess an impressively plastic genome and utilize copy number variations (CNVs) and single-nucleotide polymorphisms (SNPs) to escape drug pressure. Futhermore, studies have shown that they deploy extracellular vesicles (EVs) with a variety of key molecules as cargo, contributing not only to host-pathogen interaction & pathogenesis, but also to spread of DR. TF and DR are discussed here in detail, as well as the current state of vaccine development and available and prospective therapies for CL, MCL, VL, and CanL. Variables affecting the course of disease are addressed. Finally, the role of dogs as a reservoir for Leishmania parasites, as well as their potential to contribute to the spread of DR parasites, is considered.