1. Guinea Pig Diseases

2. Antibiotic toxicity
Antibiotics may suppress clinical signs but usually do not eliminate the organism and fatal antibiotic-induced enterocolitis is always a concern in treating guinea pigs.
Antibiotics implicated include penicillin, aminoglycoside, erythromycin, clindamycin, lincomycin, chlonetracycline, estreptomycin, bacitracin, and dihydrostreptomycin.

3. BACTERIAL AND FUNGAL DISEASES
Bacterial and fungal agents are responsible for some of the most significant diseases of guinea pigs

4. Bacterial diseases
Several primary respiratory diseases of the guinea pig are of bacterial origin, with Bordetella bronchiseptica and Streptococcus pneumoniae being the most important.
Other infectious agents act as opportunistic invaders in traumatized tissue (Streptococcus zooepidemicus), and contribute to enteric disease (Clostridium piliforme and Salmonella spp) and dermatitis (Trichophyton mentagrophytes).

5. Bordatella
Pneumonic lungs, seen here as the dark-colored tissue, may have one or more areas of consolidation and hemorrhage. Bordetella bronchiseptica, Streptococcus pneumoniae, or other bacteria frequently cause pneumonia in guinea pigs. Affected animals may have no clinical signs, or exhibit nasal discharge, sneezing, dyspnea, weight loss, or sudden death

6. Bordetella
Bordetella bronchiseptica is a small gram negative rod. Incidence of Bordetella bronchiseptica infection in guinea pigs may be high because many animal species such as rabbits, dogs and cats carry the organism in nonclinical infections. For this reason, rabbits and guinea pigs should not be housed together.
Transmission between animals is by direct contact, aerosol, or contaminated fomites

7. Bronchopneumonia
Lesions include rhinitis, tracheitis and pulmonary consolidation. Typical histopathologic lesions of purulent bronchitis and bronchopneumonia with large accumulations of neutrophils and intraluminal debris (arrow) are shown here

8. Head tilt
Otitis media may also occur with Bordetella infections. Severe otitis media may be accompanied by head tilt (torticollis).
One may detect suppurative otitis media through radiographic examination of the tympanic bulla, as illustrated in this unilaterally affected animal (arrow).

9. Bordatella
Treatment of Bordetella bronchiseptica infection is often unrewarding. Antibiotics of choice include chloramphenicol, sulfamethazine and trimethoprim- sulfa.
Effective prevention includes good husbandry and maintenance of a closed Bordetella free colony

10. Streptococcus pneumoniae
Fibrinopurulent pericarditis, shown here, can be caused by Streptococcus pneumoniae. It may be accompanied by fibrinous pleuritis and bronchopneumonia. S. pneumoniae is a gram positive.
Mortality is high
Clinical signs are similar to those seen in other bacterial pneumonias. Otitis media, metritis and other suppurative processes may occur.
Transmission of Streptococcus pneumoniae is by aerosol or direct contact with diseased or asymptomatic carrier guinea pigs, rats or humans

11. Lymphadenitis
Cervical lymphadenitis is caused most commonly by Streptococcus zooepidemicus. Other Streptococcus spp and Streptobacillus moniliformis are rarely implicated.
The organism may be an asymptomatic inhabitant of the upper respiratory track that opportunistically invades damaged mucosa.

12. Bite wounds or aerosol spread onto mucosal surfaces are the primary modes of transmission. Cervical lymph nodes become swollen, abscess and often rupture.

13. Lymphadenitis
Lymph nodes progress to encapsulated abscesses filled with yellow-white purulent exudate. Diagnosis is based on clinical signs and culture of the organism from lesions.
Treatment may include drainage and lavage of lesions and antibiotic therapy with chloramphenicol or trimethoprim-sulfa.
Control is accomplished by culling affected animals prior to rupture of lesions and separating new stock from an existing colony

14. Tyzzer’s disease
This image shows the multiple gray-white foci often found in the liver of guinea pigs with Tyzzer's disease.
See mice info….

15. Salmonellosis
Salmonella typhimurium and other Salmonella spp will infect guinea pigs. Sporadic outbreaks with high mortality are the rule, with guinea pigs becoming most susceptible around parturition, weaning, or other times of physiologic stress.
Clinical signs of salmonellosis include anorexia, rough haircoat, lethargy, weight loss, soft feces, reproductive inefficiency and abortion.

16. Transmission
Many animal species harbor Salmonella organisms which are shed intermittently in the feces. Transmission is fecal-oral; organisms often are introduced in contaminated foods such as fresh fruits and vegetables, or through the water supply.

17. Necropsy findings may include gas and fluid contents in the gastrointestinal tract as seen here. Enlargement of the liver, spleen and lymphoid tissues may also be found.

18. Salmonella
Management Culture-positive animals should be removed from the colony. The room and equipment should be disinfected and restocked with clean animals.

19. Dermatophytosis
This animal has dermatophytosis and may also show some signs of barbering. Trichophyton mentagrophytes is the most common cause of dermatophytosis (ringworm) in the guinea pig and rabbit causing patchy alopecia

20. While clinical infections are uncommon, asymptomatic carriers are abundant. Spores may be found in hair, bedding and soil

21. Diagnosis
Culture of hair shafts from a lesion onto dermatophyte test media may also be used to confirm a diagnosis.
Topical antifungal creams used daily for 2 to 4 weeks, or griseofulvin at 25 mg/kg daily in the water for 14 days or 20mg/kg in feed for 25 days, are generally effective treatments.
Prevention of outbreaks may be accomplished by strict sanitation, screening suspect animals and culling affected animals.
Trichophyton mentagrophytes is infective to humans and other animal species.

22. Mastitis
Mastitis is common in lactating sows. Milk provides an excellent media for the growth of bacteria that may invade when young traumatize the teats. Multiple agents have been implicated, including Pasteurella spp, Klebsiella spp, Staphylococcus spp, Streptococcus spp and others. Mammary glands become warm, enlarged and hyperemic, as illustrated on the image.
The milk may appear bloody; depression and even death may follow. Diagnosis is based on clinical signs.
Treatment includes hot packs and antibiotic therapy

23. VIRAL AND CHLAMYDIAL DISEASES
Some viral and chlamydial disease agents are documented, but they are of limited importance

24. Conjunctivitis
Overt signs of inclusion body conjunctivitis, as seen in this image, are found primarily in one to three week old guinea pigs. Spontaneous resolution of the disease is complete by four weeks of age in most animals. Chlamidia psittaci, the infective agent, is transmitted via feces, saliva and nasal secretions; infections may be spread by direct contact or aerosol
Zoonotic

25. Lymphosarcoma
A type Oncornavirus is the etiologic agent responsible for the leukemia found in aged guinea pigs. Cavian leukemia virus is widespread and usually transmitted transplacentally, remaining dormant in the animal until aging or stress trigger disease expression.

26. Hepatomegaly
Hepatomegaly, splenomegaly and diffuse lymphadenopathy are found frequently in guinea pigs with viral- induced leukemia/ lymphosarcoma. Enlarged organs appear mottled and light in color. Anemia and leukocytosis are often present

27. PARASITES
Many parasites are known to infect guinea pigs, but as a rule, parasites are more a problem in hobby and breeding colonies than in the research setting.

28. Ectoparasites
Common ectoparasites of the guinea pig include the mites Trixicaris caviae and Chirodiscoides caviae, as sell as the lice, Gliricola porcelli and Gyropus ovalis.

29. Acariasis
Acariasis in guinea pigs is primarily associated with two species of mite, Trixacaris caviae and Chirodiscoides caviae.
Mild to severe alopecia may be seen, as illustrated in the image

30. Trixacaris caviae, a burrowing mite, poses a significant threat to the health of a guinea pig colony.
Trixicaris caviae tend to distribute on the neck, shoulders, lower abdomen, and inner thighs, whereas Chirodiscoides caviae distribute more randomly

31. Trixacaris caviae
Trixacaris caviae, a sarcoptid mange mite, burrows through the keratin layer of the epidermis causing alopecia, crusting, and an intense pruritus that may lead to self mutilation, debility and death.

32. Chirodiscoides caviae
Chirodiscoides caviae, a fur mite, may cause few or no clinical signs in infested animals. Mites are transmitted by direct contact with the host, animal bedding, or hair and debris.

33. Treatments
Reported treatments for acariasis include pyrethroid flea powder dusts, lime sulfur dips and injections with ivermectin.

34. Lice
Guinea pig lice, Gliricola porcelli (left) and Gyropus ovalis (right) are chewing lice that cause occasional alopecia and mild pruritus with heavy infestations; Gliricola porcelli is seen more commonly. Lice are spread by direct contact with the host or contaminated bedding.