If ehrlichiosis is suspected, treatment should not be delayed while waiting for a definitive laboratory confirmation, as prompt doxycycline therapy has been associated with improved outcomes. Doxycycline is the treatment of choice.

Presentation during early pregnancy can complicate treatment.Rifampin has been used in pregnancy and in patients allergic to doxycycline.

Supportive care must be provided to animals that have clinical signs. Subcutaneous or intravenous fluids are given to dehydrated animals, and severely anemic dogs may require a blood transfusion. Treatment for ehrlichiosis involves the use of antibiotics such as tetracycline or doxycycline for a period of at least six to eight weeks; response to the drugs may take one month. Treatment with macrolide antibiotics like clarithromycin and azithromycin is being studied. In addition, steroids may be indicated in severe cases in which the level of platelets is so low that the condition is life-threatening.

Tick control is the most effective method of prevention, but tetracycline at a lower dose can be given daily for 200 days during the tick season in endemic regions.

Currently, there is no vaccine against human granulocytic anaplasmosis, so antibiotics are the only form of treatment. The best way to prevent HGA is to prevent getting tick bites.

Doxycycline is the treatment of choice. If anaplasmosis is suspected, treatment should not be delayed while waiting for a definitive laboratory confirmation, as prompt doxycycline therapy has been shown to improve outcomes. Presentation during early pregnancy can complicate treatment. Doxycycline compromises dental enamel during development. Although rifampin is indicated for post-delivery pediatric and some doxycycline-allergic patients, it is teratogenic. Rifampin is contraindicated during conception and pregnancy.

If the disease is not treated quickly, sometimes before the diagnosis, the person has a high chance of mortality. Most people make a complete recovery, though some people are intensively cared for after treatment. A reason for a person needing intensive care is if the person goes too long without seeing a doctor or being diagnosed. The majority of people, though, make a complete recovery with no residual damage.

"N. risticii" responds well to tetracycline antibiotics. Mild cases may be treated with oral doxycycline, while severe cases are usually treated with intravenous oxytetracycline.

Supportive care for severe cases is aimed at minimizing the effects of endotoxemia and preventing laminitis. This may include intravenous fluids and electrolytes to counteract the diarrhea; NSAIDs such as Banamine (flunixin meglumine); intravenous dimethyl sulfoxide; administration of products such as Biosponge or activated charcoal via nasogastric tube to bind endotoxins; polymyxin B or plasma for endotoxemia; supportive shoeing; low doses of intramuscular acepromazine; and pentoxifylline.

Doxycycline and minocycline are the medications of choice. For people allergic to antibiotics of the tetracycline class, rifampin is an alternative. Early clinical experience suggested that chloramphenicol may also be effective, however, in vitro susceptibility testing revealed resistance.

Appropriate antibiotic treatment should be started immediately when there is a suspicion of Rocky Mountain spotted fever on the basis of clinical and epidemiological findings. Treatment should not be delayed until laboratory confirmation is obtained. In fact, failure to respond to a tetracycline argues against a diagnosis of Rocky Mountain spotted fever. Severely ill patients may require longer periods before their fever resolves, especially if they have experienced damage to multiple organ systems. Preventive therapy in healthy patients who have had recent tick bites is not recommended and may, in fact, only delay the onset of disease.

Doxycycline (a tetracycline) (for adults at 100 milligrams every 12 hours, or for children under at 4 mg/kg of body weight per day in two divided doses) is the drug of choice for patients with Rocky Mountain spotted fever, being one of the only instances doxycycline is used in children. Treatment should be continued for at least three days after the fever subsides, and until there is unequivocal evidence of clinical improvement. This will be generally for a minimum time of five to ten days. Severe or complicated outbreaks may require longer treatment courses. Doxycycline/ tetracycline is also the preferred drug for patients with ehrlichiosis, another tick-transmitted infection with signs and symptoms that may resemble those of Rocky Mountain spotted fever.

Chloramphenicol is an alternative drug that can be used to treat Rocky Mountain spotted fever, specifically in pregnancy. However, this drug may be associated with a wide range of side effects, and careful monitoring of blood levels can be required.

No human vaccine is available for ehrlichiosis. Tick control is the main preventive measure against the disease. However, in late 2012 a breakthrough in the prevention of CME (canine monocytic ehrlichiosis) was announced when a vaccine was accidentally discovered by Prof. Shimon Harrus, Dean of the Hebrew University of Jerusalem's Koret School of Veterinary Medicine.

While a vaccine is available for PHF, it does not cover all strains of the bacterium, and recent vaccine failures seem to be on the rise. Additionally, the vaccine usually produces a very weak immune response, which may only lessen the severity of the disease rather than prevent it. The vaccine is administered twice a year, in early spring and in early summer, with the first one inoculation given before the mayflies emerge and the second administered as a booster.

Some veterinarians have started making recommendations for farm management to try to prevent this disease:

- Maintaining riparian barriers along bodies of water may encourage aquatic insects to stay near their places of origin

- Turning off outside lights around the barn will prevent insects from being attracted

- Cleaning water buckets and feed areas frequently and keeping food covered will reduce the chance that the horse will accidentally ingest infected insects

Tetracycline-group antibiotics (doxycycline, tetracycline) are commonly used. Chloramphenicol is an alternative medication recommended under circumstances that render use of tetracycline derivates undesirable, such as severe liver malfunction, kidney deficiency, in children under nine years and in pregnant women. The drug is administered for seven to ten days.

The treatment for bacillary angiomatosis is erythromycin given for three to four months.

No human vaccine is currently available for any tick-borne disease, except for tick-borne encephalitis. Individuals should therefore take precautions when entering tick-infested areas, particularly in the spring and summer months. Preventive measures include avoiding trails that are overgrown with bushy vegetation, wearing light-coloured clothes that allow one to see the ticks more easily, and wearing long pants and closed-toe shoes. Tick repellents containing DEET (N,N, diethyl-m-toluamide) are only marginally effective and can be applied to skin or clothing. Rarely, severe reactions can occur in some people who use DEET-containing products. Young children may be especially vulnerable to these adverse effects. Permethrin, which can only be applied to clothing, is much more effective in preventing tick bites. Permethrin is not a repellent but rather an insecticide; it causes ticks to curl up and fall off the protected clothing.

Removal of the embedded tick usually results in resolution of symptoms within several hours to days. If the tick is not removed, the toxin can be fatal, with reported mortality rates of 10–12 percent, usually due to respiratory paralysis. The tick is best removed by grasping the tick as close to the skin as possible and pulling in a firm steady manner.

Unlike the other species of ticks, the toxin of Ixodes holocyclus (Australian Paralysis Tick) will not resolve itself and will be fatal if medical assistance is not immediately sought after pulling the tick off of the animal. Contrary to popular belief, if the head detaches from the body while being pulled off, leaving the head will not inject more venom. The head may cause a skin irritation but it will not inject any more venom. Once the tick is removed, place it in a clear bag [preferably ziplock] so the vet can identify it.

Water and food can worsen the results of the animal as the venom can prevent the animal from swallowing properly. If you find an Australian Paralysis Tick on your animal, immediately remove the tick and seek veterinary assistance even if you do not think the tick has been on the animal long enough to inject venom.

Antibiotics are the primary treatment. The specific approach to their use is dependent on the individual affected and the stage of the disease. For most people with early localized infection, oral administration of doxycycline is widely recommended as the first choice, as it is effective against not only "Borrelia" bacteria but also a variety of other illnesses carried by ticks. Doxycycline is contraindicated in children younger than eight years of age and women who are pregnant or breastfeeding; alternatives to doxycycline are amoxicillin, cefuroxime axetil, and azithromycin. Individuals with early disseminated or late infection may have symptomatic cardiac disease, refractory Lyme arthritis, or neurologic symptoms like meningitis or encephalitis. Intravenous administration of ceftriaxone is recommended as the first choice in these cases; cefotaxime and doxycycline are available as alternatives.

These treatment regimens last from one to four weeks. If joint swelling persists or returns, a second round of antibiotics may be considered. Outside of that, a prolonged antibiotic regimen lasting more than 28 days is not recommended as no clinical evidence shows it to be effective. IgM and IgG antibody levels may be elevated for years even after successful treatment with antibiotics. As antibody levels are not indicative of treatment success, testing for them is not recommended.

Methicillin-resistant Staphylococcus aureus (MRSA) evolved from Methicillin-susceptible Staphylococcus aureus (MSSA) otherwise known as common "S. aureus". Many people are natural carriers of "S. aureus", without being affected in any way. MSSA was treatable with the antibiotic methicillin until it acquired the gene for antibiotic resistance. Though genetic mapping of various strains of MRSA, scientists have found that MSSA acquired the mecA gene in the 1960s, which accounts for its pathogenicity, before this it had a predominantly commensal relationship with humans. It is theorized that when this "S. aureus" strain that had acquired the mecA gene was introduced into hospitals, it came into contact with other hospital bacteria that had already been exposed to high levels of antibiotics. When exposed to such high levels of antibiotics, the hospital bacteria suddenly found themselves in an environment that had a high level of selection for antibiotic resistance, and thus resistance to multiple antibiotics formed within these hospital populations. When "S. aureus" came into contact with these populations, the multiple genes that code for antibiotic resistance to different drugs were then acquired by MRSA, making it nearly impossible to control. It is thought that MSSA acquired the resistance gene through the horizontal gene transfer, a method in which genetic information can be passed within a generation, and spread rapidly through its own population as was illustrated in multiple studies. Horizontal gene transfer speeds the process of genetic transfer since there is no need to wait an entire generation time for gene to be passed on. Since most antibiotics do not work on MRSA, physicians have to turn to alternative methods based in Darwinian medicine. However prevention is the most preferred method of avoiding antibiotic resistance. By reducing unnecessary antibiotic use in human and animal populations, antibiotics resistance can be slowed.

Rocky Mountain spotted fever can be a very severe illness and patients often require hospitalization. Because "R. rickettsii" infects the cells lining blood vessels throughout the body, severe manifestations of this disease may involve the respiratory system, central nervous system, gastrointestinal system, or kidneys.

Long-term health problems following acute Rocky Mountain spotted fever infection include partial paralysis of the lower extremities, gangrene requiring amputation of fingers, toes, or arms or legs, hearing loss, loss of bowel or bladder control, movement disorders, and language disorders. These complications are most frequent in persons recovering from severe, life-threatening disease, often following lengthy hospitalizations

Human monocytotropic ehrlichiosis (HME) is a form of ehrlichiosis associated with "Ehrlichia chaffeensis". This bacterium is an obligate intracellular pathogen affecting monocytes and macrophages.

Ehrlichiosis ewingii infection is an infectious disease caused by an intracellular bacteria, "Ehrlichia ewingii". The infection is transmitted to humans by the tick, "Amblyomma americanum". This tick can also transmit "Ehrlichia chaffeensis", the bacteria that causes human monocytic ehrlichiosis (HME).

Humans contract the disease after a bite by an infected tick of the species "Amblyomma americanum".

Those with an underlying immunodeficiency (such as HIV) appear to be at greater risk of contracting the disease. Compared to HME, ewingii ehrlichiosis has a decreased incidence of complications.

Like "Anaplasma phagocytophilum", the causative agent of human granulocytic ehrlichiosis, Ehrlichia ewingii infects neutrophils. Infection with "E. ewingii" may delay neutrophil apoptosis.

Attached ticks should be removed promptly, as removal within 36 hours can reduce transmission rates. Folk remedies for tick removal tend to be ineffective, offer no advantages in preventing the transfer of disease, and may increase the risks of transmission or infection. The best method is simply to pull the tick out with tweezers as close to the skin as possible, without twisting, and avoiding crushing the body of the tick or removing the head from the tick's body. The risk of infection increases with the time the tick is attached, and if a tick is attached for less than 24 hours, infection is unlikely. However, since these ticks are very small, especially in the nymph stage, prompt detection is quite difficult. The Australian Society of Clinical Immunology recommends against using tweezers to remove ticks but rather to kill the tick first by using a product to rapidly freeze the tick to prevent it from injecting more allergen-containing saliva. In a tick allergic person, the tick should be killed and removed in a safe place (e.g. an emergency department of a hospital).

An emerging infectious disease (EID) is an infectious disease whose incidence has increased in the past 20 years and could increase in the near future. Emerging infections account for at least 12% of all human pathogens. EIDs are caused by newly identified species or strains (e.g. Severe acute respiratory syndrome, HIV/AIDS) that may have evolved from a known infection (e.g. influenza) or spread to a new population (e.g. West Nile fever) or to an area undergoing ecologic transformation (e.g. Lyme disease), or be "reemerging" infections, like drug resistant tuberculosis. Nosocomial (hospital-acquired) infections, such as methicillin-resistant Staphylococcus aureus are emerging in hospitals, and extremely problematic in that they are resistant to many antibiotics. Of growing concern are adverse synergistic interactions between emerging diseases and other infectious and non-infectious conditions leading to the development of novel syndemics. Many emerging diseases are zoonotic - an animal reservoir incubates the organism, with only occasional transmission into human populations.

"Bartonella quintana" is transmitted by contamination of a skin abrasion or louse-bite wound with the faeces of an infected body louse ("Pediculus humanus corporis"). There have also been reports of an infected louse bite passing on the infection.

A canine vector-borne disease (CVBD) is one of "a group of globally distributed and rapidly spreading illnesses that are caused by a range of pathogens transmitted by arthropods including ticks, fleas, mosquitoes and phlebotomine sandflies." CVBDs are important in the fields of veterinary medicine, animal welfare, and public health. Some CVBDs are of zoonotic concern.

Many CVBD infect humans as well as companion animals. Some CVBD are fatal; most can only be controlled, not cured. Therefore, infection should be avoided by preventing arthropod vectors from feeding on the blood of their preferred hosts. While it is well known that arthropods transmit bacteria and protozoa during blood feeds, viruses are also becoming recognized as another group of transmitted pathogens of both animals and humans.

Some "canine vector-borne pathogens of major zoonotic concern" are distributed worldwide, while others are localized by continent. Listed by vector, some such pathogens and their associated diseases are the following:

- Phlebotomine sandflies (Psychodidae): "Leishmania amazonensis", "L. colombiensis", and "L. infantum" cause visceral leishmaniasis (see also canine leishmaniasis). "L. braziliensis" causes mucocutaneous leishmaniasis. "L. tropica" causes cutaneous leishmaniasis. "L. peruviana" and "L. major" cause localized cutaneous leishmaniasis.

- Triatomine bugs (Reduviidae): "Trypanosoma cruzi" causes trypanosomiasis (Chagas disease).

- Ticks (Ixodidae): "Babesia canis" subspecies ("Babesia canis canis", "B. canis vogeli", "B. canis rossi", and "B. canis gibsoni" cause babesiosis. "Ehrlichia canis" and "E. chaffeensis" cause monocytic ehrlichiosis. "Anaplasma phagocytophilum" causes granulocytic anaplasmosis. "Borrelia burgdorferi" causes Lyme disease. "Rickettsia rickettsii" causes Rocky Mountain spotted fever. "Rickettsia conorii" causes Mediterranean spotted fever.

- Mosquitoes (Culicidae): "Dirofilaria immitis" and "D. repens" cause dirofilariasis.

Neutrophilia is an increase in the absolute neutrophil count in the peripheral circulation. Normal blood values vary by age. Neutrophilia can be caused by a direct problem with blood cells (primary disease). It can also occur as a consequence of an underlying disease (secondary). Most cases of neutrophilia are secondary to inflammation.

Primary causes

- Conditions with normally functioning neutrophils – hereditary neutrophilia, chronic idiopathic neutrophilia

- Pelger–Huet anomaly

- Down syndrome

- Leukocyte adhesion deficiency

- Familial cold urticaria

- Leukemia (chronic myelogenous (CML)) and other myeloproliferative disorders

- Surgical removal of spleen

Secondary causes

- Infection

- Chronic inflammation – especially juvenile rheumatoid arthritis, rheumatoid arthritis, Still's disease, Crohn's disease, ulcerative colitis, granulomatous infections (for example, tuberculosis), and chronic hepatitis

- Cigarette smoking – occurs in 25–50% of chronic smokers and can last up to 5 years after quitting

- Stress – exercise, surgery, general stress

- Medication induced – corticosteroids (for example, prednisone, β-agonists, lithium)

- Cancer – either by growth factors secreted by the tumor or invasion of bone marrow by the cancer

- Increased destruction of cells in peripheral circulation can stimulate bone marrow. This can occur in hemolytic anemia and idiopathic thrombocytopenic purpura

Defined as total lymphocyte count below 1.0x10/L, the cells most commonly affected are CD4+ T cells. Like neutropenia, lymphocytopenia may be acquired or intrinsic and there are many causes. This is not a complete list.

- Inherited immune deficiency - severe combined immunodeficiency, common variable immune deficiency, ataxia-telangiectasia, Wiskott-Aldrich syndrome, immunodeficiency with short-limbed dwarfism, immunodeficiency with thymoma, purine nucleoside phosphorylase deficiency, genetic polymorphism

- Blood cell dysfunction - aplastic anemia

- Infectious diseases - viral (AIDS, SARS, West Nile encephalitis, hepatitis, herpes, measles, others), bacterial (TB, typhoid, pneumonia, rickettsiosis, ehrlichiosis, sepsis), parasitic (acute phase of malaria)

- Medications - chemotherapy (antilymphocyte globulin therapy, alemtuzumab, glucocorticoids)

- Radiation

- Major surgery

- Miscellaneous - ECMO, kidney or bone marrow transplant, hemodialysis, kidney failure, severe burn, celiac disease, severe acute pancreatitis, sarcoidosis, protein-losing enteropathy, strenuous exercise, carcinoma

- Immune dysfunction - arthritis, systemic lupus erythematosus, Sjogren syndrome, myasthenia gravis, systemic vasculitis, Behcet-like syndrome, dermatomyositis, granulomatosis with polyangiitis

- Nutritional/Dietary - alcohol abuse, zinc deficiency

Like neutropenia, symptoms and treatment of lymphocytopenia are directed at the underlying cause of the change in cell counts.