Infectious Diseases

It is important you understand the various types of common infectious diseases that companion animals may be diagnosed with. Many of these diseases can be passed from animal to animal, however, some can be passed to humans from animals, this is known as zoonoses. As an animal care worker, it is important you understand what types of infectious diseases are transmissible to both animals and people.

A zoonosis is an infectious disease caused by bacteria, viruses and parasites that can spread between animals and humans. These diseases can be transmitted from animals to humans through various means such as direct contact, contaminated food or water, and vectors like ticks and mosquitoes. It's important to follow proper hygiene and preventive measures to reduce the risk of infection.

Parasites, hosts and vectors

Parasites

A parasite is an organism that depends on another organism – the host – for its survival. Parasites can be classified into the following two main groups:

1. Internal parasites (endoparasites)
2. External parasites (ectoparasites).

Parasites are considered infectious because they are easily spread between different animals.

INTERNAL PARASITES

Internal parasites live inside the body of the host. The most common type of internal parasite in animals are types of worms.

EXTERNAL PARASITES

External parasites live on the surface of the host. Most external parasites are invertebrates (insects). Preventative treatment for external parasites typically involves spreading a liquid product on the animal’s skin. In small animals, such as cats and dogs, a topic skin preparation (a drop of medication placed directly on the skin, usually on the back of the neck) is common.

Vectors

In the context of zoonotic diseases, a vector is an organism, typically an insect like a mosquito, tick, or flea, which transmits a pathogen from one host (usually an animal) to another host (which can be another animal or a human). Vectors play a critical role in the life cycle and transmission of many zoonotic pathogens by carrying the infectious agents from infected hosts and spreading them to new hosts, thereby facilitating the spread of diseases.

Hosts

A definitive host has the parasite until its lifecycle is completed. Sexual reproduction of the parasite happens in the definitive host.

An intermediate host just has the parasite during the stage of its life where it does not reproduce sexually. The parasite moves onto a definition host for sexual reproduction.

Parasitic Worms

Parasitic worms, also known as helminths, are a diverse group of parasites that can infect both humans and domestic pets, causing a variety of health issues. Common types include roundworms, tapeworms, and hookworms. These parasites have complex life cycles that often involve multiple hosts. For instance, roundworms such as Toxocara canis in dogs and Toxocara cati in cats start their life cycle as eggs shed in the host's faeces. These eggs develop into infectious larvae in the environment, which can be ingested by another host, continuing the cycle. Tapeworms, like Dipylidium caninum, are typically transmitted when pets ingest fleas carrying the larval stage of the worm. Hookworms can penetrate the skin directly or be ingested. Transmission to humans often occurs through accidental ingestion of eggs or larvae from contaminated soil, food, water, or through direct contact with infected animals or their environments. For example, humans can contract roundworms by ingesting soil contaminated with eggs or hookworms by walking barefoot on contaminated ground. Pets can acquire these parasites through similar routes, such as ingesting contaminated materials or through direct skin contact with larvae. Effective prevention includes maintaining good hygiene, regular deworming of pets, and avoiding contact with potentially contaminated environments.

Parasitic Mites

Parasitic mites, such as those that cause scabies, are tiny insects that infect the skin of humans and domestic pets, leading to intense itching and skin irritation. The most well-known of these is Sarcoptes scabiei, responsible for scabies. The life cycle of these mites begins when a female mite burrows into the host's skin to lay eggs. These eggs hatch into larvae within a few days, which then mature into nymphs and eventually adult mites over several weeks. Mites can be transmitted to humans and pets at various stages of this life cycle. Direct skin-to-skin contact is the primary mode of transmission, making close contact between infected and uninfected individuals or animals a significant risk factor. Additionally, mites can survive for short periods on bedding, clothing, and other surfaces, facilitating indirect transmission. Effective management of scabies involves treating all affected individuals and animals, as well as thoroughly cleaning the environment to eliminate lingering mites and prevent reinfestation.

Protozoan* Parasites

Toxoplasma gondii is a protozoan parasite, which is a single-celled organism belonging to the phylum Apicomplexa. This parasite causes toxoplasmosis, a disease that can infect a wide range of warm-blooded animals, including humans. T. gondii has a complex life cycle involving both definitive and intermediate hosts.

*We briefly discussed Protozoa in a previous module when talking about classification systems. Review your learning to see what level of classification they sit in.

Life Cycle of Toxoplasma gondii:

1. Definitive Host: The definitive hosts of T. gondii are cats (domestic and wild). The sexual phase of the parasite's life cycle occurs in the intestines of the cat. Infected cats shed oocysts (a form of the parasite) in their faeces.
2. Oocyst Stage: The oocysts are excreted into the environment where they become sporulated and infectious. This can take 1-5 days. These oocysts are highly resistant and can survive in soil, water, and other environmental surfaces for long periods.
3. Intermediate Hosts: When other animals (including humans) ingest these sporulated oocysts, the parasite undergoes asexual reproduction in their tissues. This can happen through direct ingestion of contaminated soil, water, food, or via consuming undercooked meat from infected animals.
4. Tissue Cyst Stage: In intermediate hosts, the parasites form tissue cysts, primarily in muscle and brain tissues. These cysts can remain dormant for the life of the host but can reactivate if the host's immune system becomes compromised.
5. Transmission to Cats: Cats can become infected by ingesting intermediate hosts (such as rodents or birds) that harbor the tissue cysts, completing the cycle.

Transmission to Humans and Pets:

• Humans: Can become infected by ingesting oocysts from contaminated food, water, or soil, or by consuming undercooked meat containing tissue cysts. Additionally, congenital transmission can occur if a woman becomes infected during pregnancy.
• Pet: Dogs, birds, and other pets can act as intermediate hosts and become infected by ingesting oocysts from the environment ?or tissue cysts from prey animals.

Visceral larval migrans (roundworm)

What is it?

Visceral larval migrans (VLM) is a condition caused by the migration of roundworm larvae through the body's tissues. It is typically caused by Toxocara canis (dog roundworm) or Toxocara cati (cat roundworm).

How is it transmitted?

VLM is transmitted through ingestion of roundworm eggs, which are shed in the feces of infected animals. Humans, especially children, can become infected by accidentally ingesting soil, water, or food contaminated with these eggs.

What are the symptoms for animals?

Dogs and Cats: Infected animals may show signs such as diarrhea, vomiting, weight loss, pot-bellied appearance, coughing, and in severe cases, pneumonia. Puppies and kittens are more commonly affected and may exhibit poor growth and lethargy.

What are the symptoms for humans?

In humans, VLM can cause a range of symptoms depending on the organs affected by migrating larvae. Common symptoms include:

• Fever
• Fatigue
• Abdominal pain
• Coughing and wheezing
• Enlarged liver (hepatomegaly)
• Eosinophilia (high levels of a type of white blood cell)
• Neurological symptoms (in rare cases if larvae migrate to the brain)
• Eye problems (if larvae migrate to the eyes, leading to ocular larval migrans)

What animals does it affect?

• Primarily affects dogs and cats, particularly young animals (puppies and kittens).
• Humans can be accidental hosts.

What are the health risks associated with being infected by it?

In animals, severe infections can lead to significant health problems, growth retardation, and even death in young puppies and kittens.

In humans, while many infections may be asymptomatic or mild, severe cases can lead to serious health issues, including organ damage, respiratory problems, and, rarely, neurological complications or vision loss if the eyes are affected.

How is it treated?

Animals: Treatment involves the use of anthelmintic drugs such as fenbendazole, pyrantel pamoate, or milbemycin oxime. Regular deworming is recommended for puppies and kittens.
Humans: Treatment may include antiparasitic medications like albendazole or mebendazole, along with supportive care for symptomatic relief. In cases with significant organ involvement, corticosteroids may be used to reduce inflammation.

How is it prevented?

Animals: Regular deworming of pets, especially young animals, as per veterinary guidelines. Maintaining good hygiene and proper disposal of animal feces.
Humans: Avoiding contact with soil or sand that may be contaminated with animal feces, washing hands thoroughly after handling pets or soil, ensuring pets receive regular veterinary care, and educating the public about the risks and prevention methods.

Scabies

What is it?

Scabies is a highly contagious skin infestation caused by the mite Sarcoptes scabiei. These mites burrow into the skin, causing intense itching and a rash.

How is it transmitted?

Scabies is primarily transmitted through close, prolonged skin-to-skin contact with an infected person or animal. It can also spread via contaminated clothing, bedding, or furniture.

What are the symptoms for animals?

Dogs and Cats: Symptoms include intense itching, redness, rashes, hair loss, thickened skin, and secondary infections due to scratching. In dogs, it is specifically referred to as sarcoptic mange.

What are the symptoms for humans?

• Intense itching, especially at night
• Rash with small blisters or pustules
• Burrow tracks, which appear as tiny, raised, serpentine lines on the skin
• Sores caused by scratching, which can become infected
• Commonly affected areas include the wrists, elbows, armpits, waist, and between the fingers

What animals does it affect?

Scabies can affect a wide range of animals including dogs, cats, mice, rats and rabbits, although rats, mice and guinea pigs tend to be infected by mites other than Sarcoptes scabiei. Cross species transmission is possible though.

Humans can be affected by a variant of the mite adapted to humans (Sarcoptes scabiei var. hominis).

What are the health risks associated with being infected by it?

Animals: Severe itching and discomfort, leading to restlessness and decreased quality of life. Secondary bacterial infections from scratching can occur.
Humans: Intense itching and skin irritation. Secondary bacterial infections due to scratching are common. In severe cases, crusted (Norwegian) scabies can develop, which is highly contagious and more difficult to treat.

How is it treated?

Animals: Treatment includes topical or systemic acaricides such as selamectin, ivermectin, or moxidectin. Environmental decontamination is also important to prevent reinfestation.
Humans: Prescription scabicides such as permethrin cream or oral ivermectin are commonly used. All close contacts should be treated simultaneously to prevent reinfestation. Bedding, clothing, and towels should be washed in hot water and dried on high heat.

How is it prevented?

Animals: Regular veterinary check-ups, maintaining good hygiene, and avoiding contact with infected animals. Treating the environment, including bedding and living areas, is crucial.
Humans: Avoiding close contact with infected individuals, practicing good personal hygiene, and washing clothing and bedding regularly. In institutional settings, prompt treatment of outbreaks is essential to prevent spread.

Hydatid tapeworm

What is it?

The hydatid tapeworm, Echinococcus granulosus, is a parasitic tapeworm that causes hydatid disease (echinococcosis) in intermediate hosts, including humans. The adult tapeworms reside in the intestines of definitive hosts, typically dogs and other canids.

How is it transmitted?

Hydatid tapeworms are transmitted through a lifecycle involving two hosts:

• Definitive hosts: Dogs become infected by ingesting the organs of intermediate hosts that contain hydatid cysts.
• Intermediate hosts: Herbivorous animals (such as sheep, cattle, and deer) and humans become infected by ingesting eggs shed in the feces of definitive hosts. Humans often get infected through direct contact with infected dogs or contaminated soil, water, or food.

What are the symptoms for animals?

• Dogs: Usually asymptomatic, though some may have mild gastrointestinal symptoms.
• Intermediate hosts: Often asymptomatic, but severe infections can cause liver or lung issues, reduced productivity, and organ dysfunction due to large cysts.

What are the symptoms for humans?

Symptoms depend on the size, number, and location of hydatid cysts in the body, which can develop in organs such as the liver, lungs, and brain.

• Liver: Abdominal pain, nausea, vomiting, jaundice.
• Lungs: Chest pain, cough, shortness of breath.
• Other organs: Symptoms vary widely based on the affected organ.
• Cysts can rupture, leading to severe allergic reactions, anaphylaxis, and secondary infections.

What animals does it affect?

• Definitive hosts: Dogs (outside of New Zealand it affects wolves, foxes, and other canids).
• Intermediate hosts: Sheep, cattle, pigs, goats, horses, deer, and humans.

What are the health risks associated with being infected by it?

Animals: Definitive hosts are generally not severely affected, but intermediate hosts can suffer from significant organ damage, reduced productivity, and in severe cases, death.
Humans: Untreated hydatid disease can lead to life-threatening complications, including cyst rupture, severe allergic reactions, organ failure, and secondary infections. Surgical intervention is often required to remove large or symptomatic cysts.

How is it treated?

Animals: Regular deworming of dogs with appropriate anthelmintics (e.g., praziquantel) and controlling access to offal (organ meats) from livestock.
Humans: Treatment options include:

• Surgical removal of cysts.
• PAIR (puncture, aspiration, injection, and re-aspiration) technique for certain types of cysts.
• Antiparasitic medications such as albendazole or mebendazole to manage smaller cysts or as adjunct therapy post-surgery.

How is it prevented?

Animals:

• Regular deworming of dogs.
• Proper disposal of livestock offal to prevent dogs from consuming infected organs.
• Controlling stray dog populations.

Humans:

• Practicing good hygiene, including regular hand washing, especially after handling dogs or working in areas where dog feces might be present.
• Avoiding consumption of contaminated water or food.
• Educating the public about the risks of hydatid disease and the importance of controlling the lifecycle of Echinococcus tapeworms.

Ringworm

What is it?

Ringworm is a fungal infection of the skin, hair, or nails caused by dermatophytes. Despite its name, it is not caused by a worm. The infection is also known as dermatophytosis and is commonly caused by fungi of the genera Trichophyton, Microsporum, and Epidermophyton.

How is it transmitted?

Ringworm is highly contagious and can be transmitted through:

• Direct contact with an infected person or animal.
• Indirect contact with contaminated objects such as clothing, brushes, towels, or bedding.
• Contact with contaminated soil.

What are the symptoms for animals?

• Circular, hairless patches on the skin that may be red, scaly, and itchy.
• Crusting and scaling of the skin.
• Broken hairs or hair loss.
• In severe cases, lesions can spread over large areas of the body.
• Commonly affected areas include the face, ears, paws, and tail.

What are the symptoms for humans?

• Red, circular, itchy rash with a raised border and clearer center.
• Patches of hair loss if the scalp is affected.
• Thickened, discolored, or brittle nails if the infection involves the nails.
• The rash can appear on various parts of the body, including the scalp, feet (athlete’s foot), groin (jock itch), and body.

What animals does it affect?

Ringworm can affect a wide range of animals, including pets such as cats and dogs, rodents and rabbits. Ringworm is not common in birds, but cases have been recorded.

What are the health risks associated with being infected by it?

Animals: While generally not life-threatening, ringworm can cause significant discomfort and secondary bacterial infections due to scratching. It can also lead to more widespread skin infections in young, old, or immunocompromised animals.
Humans: In most cases, ringworm is not serious but can cause significant discomfort and embarrassment due to its appearance. In rare cases, secondary bacterial infections can occur.

How is it treated?

Animals:

• Topical antifungal treatments such as miconazole, clotrimazole, or lime sulfur dips.
• Oral antifungal medications like griseofulvin, itraconazole, or terbinafine for severe cases.
• Environmental decontamination to remove fungal spores.

Humans:

• Over-the-counter topical antifungal creams, lotions, or powders such as clotrimazole, miconazole, or terbinafine.
• Oral antifungal medications like terbinafine or itraconazole for severe or widespread infections.
• Keeping the affected area clean and dry.

How is it prevented?

Animals:

• Regular grooming and hygiene.
• Keeping living areas clean and disinfected.
• Isolating infected animals to prevent the spread to others.
• Regular veterinary check-ups, especially in multi-pet households or animal shelters.

Humans:

• Practicing good personal hygiene, including regular hand washing.
• Avoiding sharing personal items such as towels, clothing, or hairbrushes.
• Wearing protective clothing when handling infected animals or contaminated materials.
• Keeping skin dry and clean, especially in areas prone to moisture.
• Treating infected pets promptly to prevent transmission to humans.

Toxoplasmosis

What is it?

Toxoplasmosis is an infection caused by the very small protozoan parasite Toxoplasma gondii. It can infect most warm-blooded animals, including humans. The parasite has a complex life cycle that includes felines as the definitive hosts.

How is it transmitted?

Humans: Transmission can occur through:

• Ingesting undercooked or raw meat containing tissue cysts.
• Consuming food or water contaminated with oocysts from cat feces.
• Handling cat litter or soil contaminated with infected cat feces and then touching the mouth.
• Vertical transmission from an infected mother to her unborn child.
• Organ transplantation or blood transfusion (rare).

Animals: Transmission primarily occurs through:

• Ingesting oocysts from the environment.
• Predation or scavenging on infected intermediate hosts.

What are the symptoms for animals?

Cats: Often asymptomatic, but some may show signs such as fever, lethargy, loss of appetite, and respiratory issues.
Other Animals: Symptoms can include fever, anorexia, lethargy, pneumonia, encephalitis, and ocular issues.

What are the symptoms for humans?

Healthy Individuals: Most are asymptomatic, but some may experience flu-like symptoms such as swollen lymph nodes, muscle aches, and fatigue.
Unhealthy Individuals: Severe symptoms can occur, including encephalitis, neurological issues, eye infections, and respiratory problems.
Congenital Toxoplasmosis: If a pregnant woman is infected, the parasite can infect the fetus, leading to miscarriage, stillbirth, or congenital defects such as hydrocephalus, intellectual disabilities, and chorioretinitis.

What animals does it affect?

Affects most warm-blooded animals, including:

• Domestic cats (definitive hosts).
• Dogs, rats, mice, rabbits, parrots (less common).
• Humans (accidental hosts).

What are the health risks associated with being infected by it?

Animals: Can cause significant health issues, particularly in young or immunocompromised animals. In livestock, it can lead to economic losses due to reproductive issues.
Humans: While often mild or asymptomatic, severe cases can result in serious health problems, especially in immunocompromised individuals and congenitally infected infants.

How is it treated?

Animals: Treatment typically includes antiprotozoal drugs such as clindamycin, pyrimethamine, and sulfonamides. Supportive care may be needed for symptomatic animals.
Humans:

• Healthy Individuals: Often no treatment is needed, but symptoms can be managed with over-the-counter medications.
• Immunocompromised Individuals: Combination therapy with pyrimethamine and sulfadiazine, along with folinic acid to mitigate side effects.
• Pregnant Women: Spiramycin may be used to reduce the risk of fetal transmission, and pyrimethamine-sulfadiazine may be used if fetal infection is confirmed.

How is it prevented?

Animals:

• Preventing cats from hunting and scavenging.
• Properly disposing of cat feces.
• Feeding cats commercial or cooked food instead of raw meat.
• Regular veterinary care and monitoring.

Humans:

• Cooking meat thoroughly and practicing safe food handling.
• Washing hands and kitchen surfaces after handling raw meat.
• Avoiding consumption of unpasteurized dairy products.
• Wearing gloves while gardening or handling soil.
• Changing cat litter boxes daily and washing hands afterward.
• Pregnant women should avoid handling cat litter or ensure proper hygiene if they must.

Salmonella

What is it?

Salmonella is a genus of bacteria that causes salmonellosis, a common bacterial infection affecting the intestinal tract. There are many different types of Salmonella bacteria, which can infect both humans and animals.

How is it transmitted?

Humans: Transmission occurs through the ingestion of contaminated food or water, direct contact with infected animals or their environments, and through person-to-person contact in cases of poor hygiene.
Animals: Transmission primarily occurs through ingestion of contaminated feed or water, direct contact with infected animals, and vertical transmission from mother to offspring.

What are the symptoms for animals?

Pets (Dogs and Cats): Symptoms include vomiting, diarrhea (sometimes with blood), fever, lethargy, and abdominal pain.

What are the symptoms for humans?

Symptoms typically appear 6 hours to 6 days after infection and include:

• Diarrhea (sometimes bloody)
• Abdominal cramps
• Fever
• Nausea and vomiting
• Headache
• Muscle pain

Symptoms usually last 4-7 days, but severe cases may require hospitalization, especially in young children, the elderly, and immunocompromised individuals.

What animals does it affect?

Affects a wide range of animals, including:

• Pets (dogs, cats, rodents)
• Birds, including parrots, canaries, finches

What are the health risks associated with being infected by it?

Animals: Can lead to severe dehydration, systemic infections, and death, particularly in young or immunocompromised animals. In poultry, it can cause economic losses due to reduced productivity.
Humans: Most infections are self-limiting, but severe cases can lead to dehydration, bacteremia (bacteria entering the bloodstream), and complications such as reactive arthritis or meningitis. Vulnerable populations (infants, elderly, immunocompromised individuals) are at higher risk for severe illness and complications.

How is it treated?

Animals: Supportive care with fluids and electrolytes. Antibiotic treatment may be necessary in severe cases or for systemic infections.
Humans:

• Mild Cases: Often self-limiting and require only supportive care such as hydration and rest.
• Severe Cases: May require hospitalization for intravenous fluids and antibiotics, especially if the infection spreads beyond the intestines.

How is it prevented?

Animals:

• Maintaining good hygiene and sanitation in animal housing.
• Providing clean and uncontaminated feed and water.
• Implementing biosecurity measures to prevent the introduction and spread of infection.
• Regular veterinary check-ups and monitoring for signs of illness.

Humans:

• Cooking meat, poultry, and eggs thoroughly.
• Avoiding raw or undercooked food, especially meat, poultry, and eggs.
• Practicing good hand hygiene, especially after handling raw meat, eggs, or animals.
• Washing fruits and vegetables before eating.
• Avoiding cross-contamination in the kitchen by using separate cutting boards and utensils for raw meat and other foods.
• Drinking only pasteurized milk and juices.
• Practicing safe handling and hygiene when in contact with pets, particularly reptiles and amphibians.

Staphylococcus

What is it?

Staphylococcus is a genus of bacteria commonly found on the skin and mucous membranes of humans and animals. Some species, such as Staphylococcus aureus, can cause infections ranging from minor skin conditions to severe systemic infections.

How is it transmitted?

Humans: Transmission occurs through direct contact with infected individuals, contact with contaminated surfaces or objects, and via respiratory droplets. Healthcare settings can also be a source of transmission.
Animals: Transmission occurs through direct contact with infected animals, contaminated environments, or via wounds.

What are the symptoms for animals?

Symptoms can vary depending on the species of Staphylococcus and the site of infection:

• Skin and soft tissue infections: Redness, swelling, warmth, pain, abscesses, and pustules.
• Mastitis: Swelling, redness, and pain in the udder, decreased milk production.
• Systemic infections: Fever, lethargy, loss of appetite, and organ-specific symptoms (e.g., respiratory distress in pneumonia).
• Urinary tract infections: Increased urination frequency, straining, blood in urine.

What are the symptoms for humans?

Symptoms depend on the site and severity of the infection:

• Skin and soft tissue infections: Red, swollen, painful areas on the skin, boils, abscesses, impetigo.
• Respiratory infections: Cough, shortness of breath, fever, chest pain (in cases of pneumonia).
• Food poisoning: Nausea, vomiting, diarrhea, abdominal cramps (caused by enterotoxins produced by the bacteria).
• Systemic infections: Fever, chills, low blood pressure, organ-specific symptoms, sepsis.
• Toxic shock syndrome: High fever, rash, low blood pressure, multi-organ failure.

What animals does it affect?

A wide range of animals can be affected, including:

• Domestic pets such as dogs, cats, rabbits, mice, rats, guinea pigs.
• Companion birds such as parrots, canaries and finches
• Humans (accidental hosts).

What are the health risks associated with being infected by it?

Animals: Risks include severe skin infections, systemic infections, and conditions such as mastitis in dairy animals, leading to economic losses. Untreated infections can be life-threatening.
Humans: Risks include minor to severe skin infections, systemic infections such as sepsis, toxic shock syndrome, and complications from antibiotic-resistant strains like MRSA (Methicillin-resistant Staphylococcus aureus).

How is it treated?

Animals:

• Topical or systemic antibiotics depending on the severity and location of the infection.
• Drainage of abscesses if present.
• Supportive care such as wound cleaning and management.

Humans:

• Mild Infections: Topical antibiotics or oral antibiotics such as penicillin, cephalosporins, or clindamycin.
• Severe Infections: Intravenous antibiotics, including vancomycin for MRSA infections.
• Supportive Care: Wound care, hydration, and pain management.
• Surgical Intervention: In cases of abscesses, infected implants, or severe systemic infections.

How is it prevented?

Animals:

• Maintaining good hygiene and sanitation in animal housing.
• Promptly treating wounds and skin lesions.
• Isolating infected animals to prevent the spread of infection.
• Regular veterinary check-ups and monitoring for signs of infection.

Humans:

• Practicing good personal hygiene, including regular hand washing.
• Keeping wounds clean and covered.
• Avoiding sharing personal items such as towels and razors.
• Cleaning and disinfecting frequently touched surfaces.
• Using appropriate protective measures in healthcare settings to prevent nosocomial infections.
• Proper food handling and preparation to avoid food poisoning.

Q Fever

What is it?

Q Fever is a zoonotic disease caused by the bacterium Coxiella burnetii. It can infect a variety of animals and humans, leading to both acute and chronic illness.

How is it transmitted?

Humans: Transmission primarily occurs through inhalation of aerosols contaminated with *Coxiella burnetii* from the birth products, urine, feces, or milk of infected animals. It can also occur through direct contact with these materials or consumption of unpasteurized milk. Rarely, tick bites and human-to-human transmission can occur.
Animals: Transmission occurs through direct contact with infected animals, their birth products, or contaminated environments. Vertical transmission from mother to offspring can also occur.

What are the symptoms for animals?

Often asymptomatic but can cause reproductive issues.

• Abortion, stillbirth, premature delivery.
• Weak offspring.

What are the symptoms for humans?

Acute Q Fever (One-time occurrence):

• High fever, severe headache, fatigue, muscle pain.
• Chills, sweats, cough, chest pain.
• Nausea, vomiting, diarrhea.
• Pneumonia, hepatitis.

Chronic Q Fever (more severe, occurring months to years after initial infection):

• Endocarditis (infection of the heart valves), which is potentially life-threatening.
• Persistent fatigue, night sweats, weight loss.
• Other chronic conditions like osteomyelitis (bone infection)

What animals does it affect?

Affects a wide range of animals, including:

• Cats, dogs, rabbits, rats, mice, guinea pigs (less commonly affected).
• Parrots, canaries and finches (rare)

What are the health risks associated with being infected by it?

Animals: Economic losses due to reproductive failures in livestock. Infected animals can shed bacteria, posing a risk to other animals and humans.
Humans: Risks include severe acute illness, chronic infection leading to conditions like endocarditis, and complications in pregnant women (e.g., miscarriage, stillbirth). Q Fever can be fatal if not treated, especially in chronic cases.

How is it treated?

Animals: There is no specific treatment for Q Fever in animals. Management focuses on controlling the infection spread through good farm practices and biosecurity measures.
Humans:

• Acute Q Fever: Antibiotics such as doxycycline are the primary treatment, typically for 2-3 weeks.
• Chronic Q Fever: Long-term antibiotic therapy, often with a combination of doxycycline and hydroxychloroquine, for several months to years. Regular monitoring and follow-up are necessary.

How is it prevented?

Animals:

• Implementing biosecurity measures to reduce the spread of infection.
• Proper disposal of birth products and other contaminated materials.
• Regular health monitoring and vaccination (where available, e.g., for sheep and goats in some countries).

Humans:

• Avoiding contact with birth products, urine, feces, and milk of potentially infected animals.
• Using protective equipment (masks, gloves) when handling animals or contaminated materials.
• Consuming only pasteurized dairy products.
• Implementing environmental controls to reduce aerosolization of the bacteria.
• Vaccination for at-risk populations (e.g., people working with livestock) where vaccines are available.

Psittacosis (Parrot Fever)

Caused by the bacterium Chlamydia psittaci, it can be transmitted to humans through inhalation of dust from dried bird droppings, feathers, and respiratory secretions. In humans, it can cause flu-like symptoms and respiratory issues.

In New Zealand, as in many other countries, psittacosis is a notifiable disease, meaning that cases must be reported to health authorities. This helps in monitoring and controlling outbreaks. Birds in New Zealand, particularly those in close contact with humans, such as pet birds and those in aviaries, can be carriers of Chlamydia psittaci.

Preventive measures for psittacosis include:

• Ensuring good hygiene practices when handling birds.
• Regular veterinary check-ups for pet birds to monitor their health.
• Quarantining new birds before introducing them to existing ones.
• Using personal protective equipment when cleaning bird cages or handling birds, especially if they are sick.

If someone in New Zealand suspects they or their birds may have psittacosis, they should seek medical or veterinary advice promptly.

Avian Influenza

Various strains of avian influenza viruses can infect humans who have close contact with infected birds. Symptoms in humans range from mild respiratory issues to severe illness. New strains often make the news, especially since the covid pandemic: for example, in April and May 2024 a new strain of H1N1 influenza started showing signs of spreading around the world and being transmissible between humans and birds.

Pet canaries, finches, and parrots have the potential to transmit avian influenza (bird flu) to humans, although the risk is generally considered to be low. Avian influenza is primarily a concern with poultry and wild birds, but pet birds can also be affected. In New Zealand, as in other countries, there are measures in place to monitor and control avian influenza outbreaks to protect both animal and human health.

Key Points About Avian Influenza Transmission:

Species Susceptibility: While all bird species can potentially carry avian influenza viruses, the risk of transmission to humans is more commonly associated with close contact with infected poultry. Pet birds like canaries, finches, and parrots are less commonly involved in human infections.
Transmission to Humans: Humans can contract avian influenza through direct contact with infected birds, their droppings, or secretions. This can happen through handling, cleaning cages, or exposure to contaminated surfaces. Inhalation of aerosolized particles from dried feces or respiratory secretions is also a potential route of transmission.
Symptoms in Birds: Infected birds may show symptoms such as respiratory distress, diarrhea, swelling around the eyes and neck, and sudden death. However, some birds can be asymptomatic carriers, meaning they can spread the virus without showing any signs of illness.
Symptoms in Humans: In humans, avian influenza can cause a range of symptoms from mild respiratory illness to severe pneumonia and even death, depending on the virus strain involved.

Preventive Measures:

• Hygiene: Maintain good hygiene practices, such as regular hand washing after handling birds or cleaning their cages.
• Health Monitoring: Keep an eye on the health of pet birds and consult a veterinarian if they show signs of illness.
• Protective Gear: Use protective gear, like gloves and masks, when cleaning bird cages or handling sick birds.
• Avoid Wild Birds: Limit contact between pet birds and wild birds, which are more likely to carry avian influenza viruses.
• Monitoring and Reporting: New Zealand has strict biosecurity measures to monitor and control avian influenza. If avian influenza is suspected in pet birds, it should be reported to local veterinary authorities to help prevent the spread of the virus.

Cryptococcosis

Caused by the fungus Cryptococcus neoformans, which is found in bird droppings, especially from pigeons. Inhalation of contaminated dust can lead to lung infections and, in severe cases, spread to the central nervous system. Cryptococcosis can be spread by pet parrots, canaries, and finches in New Zealand, although it is relatively uncommon.

Transmission:

• The primary source of Cryptococcus fungi is bird droppings. While pigeons are the most common carriers, other birds, including parrots, canaries, and finches, can also carry and shed the fungus in their droppings.
• Inhalation: Humans and other animals can contract cryptococcosis by inhaling the airborne fungal spores from dried bird droppings. The spores can become aerosolized and pose an infection risk, especially in enclosed or poorly ventilated spaces.

Symptoms in Humans

Cryptococcosis primarily affects the lungs and the central nervous system. Symptoms can include cough, chest pain, shortness of breath, fever, headache, neck stiffness, and sensitivity to light if it progresses to meningitis.

Symptoms in Birds

Birds often do not show symptoms of cryptococcosis, making it difficult to detect. However, they can still shed the fungus in their droppings.

Preventive Measures

• Hygiene: Regularly clean bird cages and surrounding areas to minimize the accumulation of droppings. Use protective gear such as gloves and masks when cleaning.
• Ventilation: Ensure good ventilation in areas where birds are kept reducing the concentration of airborne spores.
• Health Monitoring: Regularly monitor the health of pet birds and consult a veterinarian if they show any signs of illness.
• Environmental Control: Minimize exposure to areas with large amounts of bird droppings, especially pigeon droppings, which are more commonly associated with cryptococcosis.

Biosecurity Measures

New Zealand has biosecurity measures in place to monitor and control fungal infections and other zoonotic diseases. If cryptococcosis is suspected in pet birds, it is advisable to seek veterinary advice for proper diagnosis and management.

Histoplasmosis

Caused by the fungus Histoplasma capsulatum, which can be found in environments contaminated with bird droppings. Inhalation of spores can lead to respiratory infections. The likelihood of pet parrots, canaries, and finches in New Zealand spreading histoplasmosis is relatively low, especially if they are kept in clean, indoor environments.

Preventative and Biosecurity measures for this disease are similar to that of Cryptococcosis.

Activity

Let’s review what we have covered regarding infectious/zoonotic diseases. Download this worksheet and check ✓ in each box which animals are affected by each of the listed diseases. You will need to refer back to the learning content to make sure you check ✓ the correct boxes.

Summary

The purpose of this topic has been to look at the most common zoonotic diseases in New Zealand, what animals they infect, what the symptoms of infections are, and the treatment options available. The next topic introduces the forms of treatments that are given to animals, depending on the type of condition that they have. Me ruku ki te kaupapa, let’s go take a look.