Livestock Zoonoses: A Comprehensive Overview of Bacterial and Parasitic Diseases Transmitted from Farm Animals

Introduction

Livestock serve as reservoirs for a wide array of zoonotic pathogens, including bacteria, parasites, and viruses, that can be transmitted directly or indirectly to humans [55]. More than 60% of human pathogens are zoonotic in origin, and many emerge from domestic animal populations [55]. The intensification of animal production, global trade, and environmental change have increased the risk of spillover events [55, 91]. Zoonotic diseases impose substantial economic burdens on the livestock industry through production losses, trade restrictions, and control costs [1, 97], while also threatening public health. This article provides a comprehensive review of the major bacterial and parasitic zoonoses associated with farm animals, focusing on their biology, transmission mechanisms, diagnostic approaches, and control within a One Health framework [60, 74].

Bacterial Zoonoses

Campylobacteriosis

Campylobacter spp., particularly Campylobacter jejuni, are among the most frequently reported zoonotic bacterial pathogens worldwide, predominantly associated with poultry, cattle, and swine [59]. Colonization of the avian intestinal tract is often asymptomatic, yet contaminated carcasses serve as major sources for human infection [59]. Genetic diversity among C. jejuni isolates from farm animals and the farm environment is high, indicating multiple transmission pathways [48]. The pathogen invades the intestinal epithelium through flagella-mediated motility and adhesins, triggering an inflammatory response [59]. Detection relies on selective culture under microaerobic conditions or on molecular methods such as PCR [59]. Control measures include biosecurity, feed additives, and vaccination, though antibiotic resistance is an increasing concern [59].

Salmonellosis

Non-typhoidal Salmonella enterica serovars, including Salmonella Typhimurium and Salmonella Enteritidis, are major foodborne zoonoses transmitted from livestock, particularly poultry, pigs, and cattle [59]. Animals often carry the pathogen without clinical signs, shedding it in feces and contaminating the environment [2, 59]. Salmonella invades M cells and enterocytes via a type three secretion system, causing enteritis and systemic infection [59]. Diagnosis is by culture, serotyping, or PCR [59]. Antimicrobial resistance in Salmonella from farm animals is a global challenge, with multiresistant clones emerging in many regions [2]. Integrated surveillance under a One Health approach is essential to monitor resistance trends [3].

Listeriosis

Listeria monocytogenes is a zoonotic pathogen harbored in ruminants, particularly sheep and cattle, where it can cause encephalitis and abortion [59]. It is shed in milk and feces and can contaminate silage, leading to infection in humans through dairy products or meat [59]. The bacterium survives cold temperatures and low pH, resisting gastric acidity [59]. Diagnosis involves culture from cerebrospinal fluid or tissues, and molecular subtyping aids epidemiological investigations [59].

Q Fever (Coxiellosis)

Coxiella burnetii, the causative agent of Q fever, is a highly infectious, Gram-negative intracellular bacterium primarily associated with cattle, sheep, and goats [58]. Infected animals shed the organism in birth products, urine, milk, and feces, with aerosol transmission to humans being a major route [58]. Bulk tank milk seroprevalence in endemic areas can exceed 60%, as observed in northwestern Spain [58]. Risk factors include herd size, purchase of livestock, and geographical area [58]. Infection in dairy herds is linked to reduced conception rates and increased endometritis [58]. Diagnosis relies on serology (ELISA) or PCR [58]. Control emphasizes vaccination of livestock, biosecurity, and management of parturient materials.

Leptospirosis

Leptospirosis, caused by pathogenic Leptospira spp., is a widespread zoonosis maintained by livestock, particularly cattle, pigs, and sheep, which act as reservoir hosts [4]. Rodents are also important maintenance hosts [4]. The bacteria are shed in urine and survive in water, infecting humans and animals through mucous membranes or abraded skin [4]. Diagnosis is through dark-field microscopy, culture, serology (microscopic agglutination test), or PCR [4]. Prevention includes vaccination of livestock, rodent control, and environmental hygiene.

Brucellosis

Brucella abortus, B. melitensis, and B. suis cause brucellosis in cattle, sheep/goats, and pigs, respectively, and are important zoonoses [35, 55]. The bacteria localize in the reproductive tract, causing abortion and infertility, and are shed in high numbers in placental tissues and milk [35]. Human infection occurs through direct contact with infected animals or consumption of unpasteurized dairy products [35]. Diagnosis employs serological tests (Rose Bengal, ELISA) and culture. Control relies on test-and-slaughter strategies, vaccination (e.g., B. abortus strain 19), and pasteurization.

Antimicrobial Resistance and ESBL-Producing Escherichia coli

Commensal Escherichia coli in livestock can acquire resistance genes, including extended-spectrum beta-lactamases (ESBLs), which pose a zoonotic risk via food chain contamination [96]. E. coli is a bioindicator of antimicrobial resistance in farm environments [96]. Studies in duck and dairy farms reveal high prevalence of resistance genes such as sul1 and blaCTX-M [5, 42]. Monitoring antimicrobial use and resistance is critical for preserving antibiotic efficacy [6, 3, 34].

Other Notable Bacterial Zoonoses

Yersinia enterocolitica is transmitted from pigs and other animals, causing enteritis [59]; Anaplasma phagocytophilum is a tick-borne bacterium infecting livestock and humans, often detected alongside protozoan parasites [50]; Streptococcus suis serotype 2 is a major pig-associated zoonotic pathogen causing meningitis; and Mannheimia haemolytica and Pasteurella multocida, while primarily animal pathogens, can cause opportunistic infections in humans [80]. Tick-borne rickettsiae such as Rickettsia species are also emerging zoonotic threats [82].

Parasitic Zoonoses

Toxoplasmosis

Toxoplasma gondii is a globally distributed protozoan parasite with a complex life cycle involving felids as definitive hosts and warm-blooded animals as intermediate hosts [7, 71]. Livestock, especially pigs, sheep, and goats, can harbor tissue cysts and contribute to human infection through consumption of undercooked meat [7, 31, 45]. Seroprevalence varies widely; in the Tavush region of Armenia, 39% of small ruminants, 28.6% of pigs, and 8.9% of cattle tested positive [45]. Risk factors include cat presence, contaminated feed, and pasture access [7]. Diagnosis is by serology (ELISA) using recombinant antigens or by PCR [31]. Economic losses arise from reproductive failure, particularly in small ruminants [7]. Control involves biosecurity to prevent cat fecal contamination, feed management, and meat hygiene.

Cryptosporidiosis and Giardiasis

Cryptosporidium spp. and Giardia duodenalis are zoonotic protozoan parasites shed by livestock, particularly calves and lambs [33]. They contaminate water sources and cause diarrheal disease in humans. Molecular typing reveals zoonotic subtypes: Cryptosporidium parvum is commonly found in cattle, and G. duodenalis assemblages A and B occur in humans and animals [33]. Diagnosis is by microscopic examination of fecal smears, immunofluorescence, or PCR [33]. Control focuses on hygiene, water treatment, and reducing fecal contamination.

Echinococcosis

Cystic echinococcosis caused by Echinococcus granulosus is a major cestode zoonosis transmitted between dogs (definitive host) and livestock (intermediate hosts, especially sheep) [8]. In endemic regions of Iran, dog reinfection with E. granulosus after praziquantel treatment was 17% at 12 months, indicating intense transmission [8]. The parasite causes hydatid cysts in the liver and lungs of livestock, leading to organ condemnation and economic loss [9]. Diagnosis in dogs is by copro-PCR or microscopy [8]. Control requires regular deworming of dogs, proper disposal of offal, and health education [10].

Trichinellosis

Trichinella spp. infect pigs and wild boar, with human cases linked to consumption of raw or undercooked meat [37, 53]. Larvae encyst in striated muscle, and diagnosis in live animals is serological; meat inspection uses artificial digestion [116]. Surveillance in wildlife and free-range pig operations is essential to prevent outbreaks.

Fasciolosis

Fasciola hepatica and F. gigantica are liver flukes transmitted by lymnaeid snails, causing significant production losses in cattle and sheep [37, 92, 97]. The economic burden of fasciolosis in Europe is estimated at over €500 million annually [97]. Infection occurs through ingestion of metacercariae on contaminated herbage. Diagnosis is by fecal sedimentation, coproantigen ELISA, or pooled PCR [11, 92]. Anthelmintic resistance, particularly to triclabendazole, is an emerging challenge [38]. Control integrates snail management, pasture rotation, and targeted treatment.

Soil-Transmitted Helminths

Ascaris suum, Trichuris suis, and hookworm species are common in pigs and ruminants and can cause zoonotic infections, especially in areas with poor sanitation [12, 47, 99]. A. suum is antigenically similar to A. lumbricoides and may contribute to human ascariasis. Diagnosis uses the Kato-Katz method or molecular tools such as next-generation sequencing-based PCR assays [75]. Mass drug administration in endemic communities is the primary control strategy, but there is evidence of benzimidazole resistance in some settings [99].

Tick-Borne Parasitic Diseases

Babesiosis, theileriosis, and anaplasmosis are caused by protozoan and rickettsial agents transmitted by ixodid ticks, posing significant health threats to livestock and a zoonotic risk for some babesial species [61, 64]. Babesia divergens and B. microti can infect splenectomized or immunocompromised humans. Theileria annulata and T. parva cause tropical theileriosis and East Coast fever, respectively, in cattle [13, 127]. Diagnosis is by blood smear examination, serology, and PCR [64]. Control includes tick management, acaricides, and vaccination (e.g., for T. annulata).

Other Parasitic Zoonoses

Leishmania spp. (affecting dogs and cattle), Trypanosoma spp. (causing surra and nagana), and Dirofilaria immitis (heartworm in dogs and occasionally humans) are additional zoonotic parasites with livestock or companion animal reservoirs [30, 84, 94]. The role of insects as mechanical vectors is also noteworthy; house flies in slaughterhouses can carry Giardia, Entamoeba, and cestode eggs [102]. Edible insects used as feed may harbor zoonotic parasites, underscoring the need for monitoring [14].

Diagnostic Approaches

Microscopy remains the cornerstone for parasitic diagnosis, especially in low-resource settings, for the detection of eggs, oocysts, and larvae [15]. However, PCR techniques offer higher sensitivity and specificity, particularly for detecting low-level infections and differentiating species [15, 75]. Next-generation sequencing (NGS) has revolutionized parasite profiling and detection of resistance markers, allowing comprehensive analysis of pathogen populations [40, 75]. Serological methods such as ELISA are widely used for bacterial zoonoses (e.g., Coxiella burnetii, Brucella spp.) and for toxoplasmosis in livestock [31, 58].

Ultrasonography is increasingly employed in veterinary parasitology for visualizing lesions caused by helminths, such as liver fluke cysts and hydatid cysts [11]. Point-of-care tests, including lateral flow immunochromatographic assays, facilitate field diagnosis [15]. In bacterial diseases, culture and antimicrobial susceptibility testing remain essential, but molecular detection of resistance genes (e.g., sul1, blaCTX-M) is rapidly expanding [42, 96].

Workflow for Zoonotic Disease Surveillance

The following Mermaid diagram illustrates a One Health surveillance workflow for detecting and managing livestock zoonoses:

graph TD
    A[Livestock Population] -->|Sampling: feces, blood, milk, tissues| B(Diagnostic Laboratory)
    B --> C{Primary Screening}
    C -->|Bacteria| D[Culture + MALDI-TOF / PCR]
    C -->|Parasites| E[Microscopy / Fecal Float / PCR]
    D --> F{Antimicrobial Susceptibility?}
    F -->|Yes| G[AST + Resistance Gene Detection]
    F -->|No| H[Pathogen Identification]
    E --> I[Egg/Oocyst Count or Molecular Typing]
    G --> J[Data Integration]
    H --> J
    I --> J
    J --> K[One Health Surveillance Database]
    K --> L[Risk Assessment & Mapping]
    L --> M["Intervention: Vaccination, Deworming, Biosecurity"]
    M --> A
    K --> N[Public Health Alert] 

Control and Prevention Strategies

Control of zoonotic zoonoses demands a One Health approach that integrates veterinary, medical, and environmental sectors [60, 74]. Key measures include:

• Biosecurity: Preventing pathogen introduction and spread through quarantine, sanitation, and pest control [56].
• Vaccination: Available for brucellosis, leptospirosis, Q fever, and some parasitic diseases (e.g., Eimeria vaccines in poultry) [1].
• Antimicrobial Stewardship: Rational use of antibiotics to mitigate resistance, supported by surveillance programs [6, 3, 16].
• Anthelmintic Management: Rotational drug classes and diagnostic monitoring to delay resistance [70, 139].
• Education and Extension: Training farmers and veterinarians in zoonotic recognition and prevention [35, 70].
• Genetic Selection: Breeding livestock for disease resistance or tolerance as a long-term strategy [1].

Waste management and composting can reduce environmental contamination, while integrated pest management limits vector populations [44].

Conclusions

Bacterial and parasitic zoonoses from livestock represent a persistent and evolving threat to animal and human health worldwide. Understanding the complex transmission pathways, pathogen biology, and ecological drivers is essential for effective control. Advances in molecular diagnostics, genomic surveillance, and computational modeling are providing powerful tools for early detection and intervention [40, 103]. A sustained commitment to One Health collaboration, combined with prudent antimicrobial use and biosecurity, is critical to reducing the burden of these diseases.

References

[1] Hu G, Do D, Gray J et al. Selection for Favorable Health Traits: A Potential Approach to Cope with Diseases in Farm Animals. Animals. 2020. URL: https://www.semanticscholar.org/paper/b370171c5a5e6e4c2ed81f79be974f6330be171f

[2] Rabello RF, Bonelli RR, Penna BA et al. Antimicrobial Resistance in Farm Animals in Brazil: An Update Overview. Animals. 2020. URL: https://www.semanticscholar.org/paper/11ec6f6c4fe4366d1b61e56e78ed82a60e40f8de

[3] Delpy L, Astbury CC, Aenishaenslin C et al. Integrated surveillance systems for antibiotic resistance in a One Health context: a scoping review. BMC Public Health. 2024. URL: https://pubmed.ncbi.nlm.nih.gov/38937706/

[4] Akanbi OB, Ola-fadunsin S, Yahaya S et al. Parasites and Parasitic Diseases of Laboratory Animals in Plateau State Nigeria: The zoonotic implications. J Parasit Dis. 2021. URL: https://www.semanticscholar.org/paper/dfc0c1e4a136dfa5dd0e6163d7247dc51dbf38bc

[5] Liu K, Wang M, Zhang Y et al. Distribution of antibiotic resistance genes and their pathogen hosts in duck farm environments in south-east coastal China. Appl Microbiol Biotechnol. 2024. URL: https://pubmed.ncbi.nlm.nih.gov/38229327/

[6] Delpy L, Astbury CC, Kavulikirwa OK et al. Exploring antibiotic stewardship interventions within a One Health context: a scoping review. Front Public Health. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/41668857/

[7] Stelzer S, Basso W, Silván JB et al. Toxoplasma gondii infection and toxoplasmosis in farm animals: Risk factors and economic impact. Food Waterborne Parasitol. 2019. URL: https://www.semanticscholar.org/paper/2da760bd61d51b6b3fc32109d54b6205ef140d3c

[8] Borhani M, Mohammadi MA, Entezami M et al. Reinfection of farm dogs following praziquantel treatment in an endemic region of cystic echinococcosis in southeastern Iran. PLoS Negl Trop Dis. 2024. URL: https://www.semanticscholar.org/paper/71549deb02ad9b515c80bdc416b4ad95a3898bb5

[9] Ola-fadunsin S, Uwabujo PI, Halleed IN et al. Prevalence and financial loss estimation of parasitic diseases detected in slaughtered cattle in Kwara State, North-central Nigeria. J Parasit Dis. 2019. URL: https://www.semanticscholar.org/paper/5fb670b3c129ca0b359bae207b3e8ab27013eb5d

[10] Arshad MF, Abbas I, Porcu F et al. Breaking the cycle of parasitic diseases with edutainment: The intersection of entertainment and education. PLoS Negl Trop Dis. 2025. URL: https://www.semanticscholar.org/paper/f062f9fc67c5f0c3ce9c2881878611aa54b55df9

[11] Corda A, Corda F, Secchi V et al. Ultrasonography of Parasitic Diseases in Domestic Animals: A Systematic Review. Animals. 2022. URL: https://www.semanticscholar.org/paper/127928aafe705f403bf36e6638741debe3ff8bfe

[12] Huang SY, Lai Y, Fang YY. The spatial-temporal distribution of soil-transmitted helminth infections in Guangdong Province, China: A geostatistical analysis of data derived from the three national parasitic surveys. PLoS Negl Trop Dis. 2022. URL: https://www.semanticscholar.org/paper/0521f6e4c0defd3fe0d25eae85104403fac63e4f

[13] Verma A, Singh SK. Control and therapeutic management of bovine tropical theileriosis in crossbred cattle. J Parasit Dis. 2016. URL: https://www.semanticscholar.org/paper/9092dab6b10a4c5ed7afed7bafed7fe5ecdf0534

[14] Gałęcki R, Sokół R. A parasitological evaluation of edible insects and their role in the transmission of parasitic diseases to humans and animals. PLoS ONE. 2019. URL: https://www.semanticscholar.org/paper/ebe9be7db024ad5d23fdb4358ff9a5657407ef0a

[15] Momčilović S, Cantacessi C, Arsić-Arsenijević V et al. Rapid diagnosis of parasitic diseases: current scenario and future needs. Clin Microbiol Infect. 2019. URL: https://www.semanticscholar.org/paper/0aab0d61c0ec7914d10bcecdf045b4e376d7a80b

[16] Zamojska D, Nowak A, Nowak I et al. Probiotics and Postbiotics as Substitutes of Antibiotics in Farm Animals: A Review. Animals. 2021. URL: https://www.semanticscholar.org/paper/7dc5ff7dec3380efada624e52c77b7d7a56e4a80

[17] Adamu A, Reyer F, Lawal N et al. Aetiologies of bacterial tick-borne febrile illnesses in humans in Africa: diagnostic limitations and the need for improvement. Front Med (Lausanne). 2024. URL: https://pubmed.ncbi.nlm.nih.gov/39351006/

[18] VanderWaal K, Deen J. Global trends in infectious diseases of swine. Proc Natl Acad Sci U S A. 2018. URL: https://pubmed.ncbi.nlm.nih.gov/30348781/

[19] Tifonova I, Lazarova L, Tchakarova S et al. TRACKING TWO-WAY HUMAN-MINK TRANSMISSION DURING AN OUTBREAK OF SEVERE ACUTE RESPIRATORY SYNDROME CORONAVIRUS 2 ON A FARM IN BULGARIA. Problems of infectious and parasitic diseases. 2025. URL: https://www.semanticscholar.org/paper/5a59d6bc4401d5ffde771d0c452a93bfc778dda4

[20] Friedman M, Xu AM, Lee R et al. The Inhibitory Activity of Anthraquinones against Pathogenic Protozoa, Bacteria, and Fungi and the Relationship to Structure. Molecules. 2020. URL: https://www.semanticscholar.org/paper/c006f52f6758bac7da0bbe83b8d8a0edb365f054

[21] Florin-Christensen M, Schnittger L. Parasitic Protozoa of Farm Animals and Pets. Cambridge International Law Journal. 2018. URL: https://www.semanticscholar.org/paper/681da9a2a9f4da51ce20d4c8145e96ae871e686e

[22] Sadr S, Simab PA, Kasaei M et al. Potential of Anthelmintic Herbal Drugs against Gastrointestinal Nematodes in Farm Animals: A Review. Farm Animal Health and Nutrition. 2022. URL: https://www.semanticscholar.org/paper/e04e6d83cf7b50fb9d27524dd92c45c353b1836e

[23] Moemenbellah-Fard M, Shahriari B, Azizi K et al. Faunal distribution of fleas and their blood-feeding preferences using enzyme-linked immunosorbent assays from farm animals and human shelters in a new rural region of southern Iran. J Parasit Dis. 2016. URL: https://www.semanticscholar.org/paper/f6b9413ae4445dc08c639055b13d7a8eac1c6f45

[24] Hull TG. Diseases Transmitted from Animals to Man. Indian Med Gaz. 1930. URL: https://www.semanticscholar.org/paper/f43b09bf62c943ceaacd5014c9842614821bbc69

[25] Neethirajan S. Transforming the Adaptation Physiology of Farm Animals through Sensors. Animals. 2020. URL: https://www.semanticscholar.org/paper/6496796058ab496d34f11e366a5b031d99ed9e31

[26] Zhang Y, Chen G, Zhou S et al. APDDD: Animal parasitic diseases and drugs database. Comp Immunol Microbiol Infect Dis. 2023. URL: https://www.semanticscholar.org/paper/ebb3f1ed9aa19d334addfe356e0da4c88a4d3c5a

[27] Ponnampalam E, Kiani A, Santhiravel S et al. The Importance of Dietary Antioxidants on Oxidative Stress, Meat and Milk Production, and Their Preservative Aspects in Farm Animals. Animals. 2022. URL: https://www.semanticscholar.org/paper/1f9274c352a909d1d2ea1343e2f87a681ebebc55

[28] Windsor P. Role of Topical Anaesthesia in Pain Management of Farm Animals, a Changing Paradigm. Animals. 2022.

Disclaimer: This article is for educational and informational purposes only. It is not intended to substitute for professional veterinary advice, diagnosis, treatment, or regulatory guidance. Always consult a licensed veterinarian or qualified specialist regarding animal health, disease diagnosis, and therapeutic decisions.