1. Introduction

Gestation in bitches has an average duration of 60 days and cats can get up to 65 days on average. These periods of pregnancy are dependent on factors such as: number of puppies, previous pregnancies, among other. The pregnancy loss can occur at any stage of pregnancy depending on the primary cause. Among these causes we can mention infectious (bacterial, viral, fungal and protozoal) and noninfectious (trauma, drugs, congenital and genetic disorders) and the neonatal death may occur in up to 3 weeks after birth.¹

1.1. Abortion and Neonatal Death from Infectious Causes

1.1.1. Herpesvirus

Canine herpesvirus can lead to abortion, stillbirth and embryonic resorptions. A pregnant bitch can become infected through direct contact with mucosal secretions (respiratory or genital). Neonatal infection usually occurs at birth; however, transplacental infection can occur and lead to mummified or dead fetuses, stillbirth, or birth of weak puppies.² Reproductive failure due to herpesvirus is characterized by infertility (early unnoticed embryonic loss), resorption (non-expulsed fetuses before ossification/calcification), abortion (expulsion of well-developed and generally calcified fetuses not expected to live outside the uterus), stillbirth (expulsion of well-developed near term fetuses that would be expected to survive outside the uterus), delivery of poorly developed and compromised neonates, or neonatal death.³ Clinical presentations include sudden death, lethargy, and excessive crying. Herpesviral infection in dogs is usually easy to diagnose on postmortem examination and is characterized by multiorgan haemorrhages, the most notable of which are seen in the kidney, lung, and liver.⁴

Viral agents are the most commonly reported infectious causes of abortion in queens. Implicated viruses include feline panleukopenia virus (FPLV), feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), feline enteric corona virus (FECV), and feline herpesvirus type 1 (FHV1).⁶

1.1.2. Brucella canis

Brucella canis is a small, gram-negative intracellular coccobacilli. Infection can cause infertility, early embryonic death, fetal resorptions, and late-term abortion.⁷

1.2. Abortion and Neonatal Death from Noninfectious Causes

1.2.1. Traumas

Traumatic causes of abortion in dogs and cats can be further subdivided into trauma during parturition, such as with dystocia, and trauma occurring after birth.¹

1.2.2. Congenital Causes

Congenital defects can be sporadic and without direct cause, can be a phenotypic reflection of a genetic disease, or can be related to toxin ingestion.⁸

1.2.3. Nutritional Deficiencies

Energy and vitamin demands increase during pregnancy. If these are deficient, fetal survival may be compromised.

1.2.4. Iatrogenic Exposure to Drugs or Other Toxic Compounds

Many drugs have been shown to potentially or clearly affect pregnancy. Drugs which may prevent maintenance of pregnancy in the dog are numerous and include members of the following families: androgens, anabolic and estrogenic steroids, glucocorticoids, antimicrobials, antifungals, antiparasitics, antineoplastic agents, analgesics, anti-inflammatories, anesthetics, gastrointestinal, cardiovascular.⁶

2. Conclusion

Pregnancy losses in both dogs and cats are important problems for breeders, considering that many animals are imported and can install a disease that initially was not in the locality. Research is still warranted to provide further improvements and reduce the incidence of pregnancy losses in dogs and cats.

References

1.  Lamm CG, Njaa BL. Clinical Approach to Abortion, Stillbirth, and Neonatal Death in Dogs and Cats.

2.  Ronsse V, Verstegen J, Thiry E, Onclin K, Aeberle C, Brunet S, et al. Canine herpesvirus-1 (CHV-1): clinical, serological and virological patterns in breeding colonies. Theriogenology. 2005;(64):61–74.

3.  Givens MD, Marley MSD. Infectious causes of embryonic and fetal mortality. Theriogenology. 2008;(70):270–285.

4.  Hashimoto A, Hirai K, Yamaguchi T, et al. Experimental transplacental infection of pregnant dogs with canine herpesvirus. Am J Vet Res. 1982;(43):844–850.

5.  Johnson CA, Walker RD. Clinical signs and diagnosis of Brucella canis infection. Compend Contin Educ. 1992;(14):763–773.

6.  Verstegen J, Dhaliwal G, Verstegen-Onclin K. Canine and feline pregnancy loss due to viral and non-infectious causes: a review. Theriogenology. 2008;(70):304–319.

7.  Graham EM, Taylor DJ. Bacterial reproductive pathogens of cats and dogs. Vet Clin Small Anim. 2012;(42):561–582.

8.  Root Kustritz MV. Clinical management of pregnancy in cats. Theriogenology. 2006;(66):145–150.