A dose-finding, long-term study on the use of calcium chloride in saline solution as a method of nonsurgical sterilization in dogs: evaluation of the most effective concentration with the lowest risk

0 Department of Emergency and Organ Transplantation (DETO), Section of Veterinary Clinic and Animal Production, University of Bari Aldo Moro , SP per Casamassima km 3, 70010 Valenzano BA , Italy 1 Department of Veterinary Science, University of Messina , Polo Universitario dell'Annunziata, Viale Annunziata, 98168, Messina , Italy 2 Parsemus Foundation , PO Box 2246, 94702 Berkeley CA , USA Background: Canine overpopulation is a global issue with serious health and welfare implications. Nonsurgical methods of sterilization could yield positive impacts on this problem, but no long-term data on such methods are available. The objective of the current investigation was to determine the effects of intratesticular injections of calcium chloride dihydrate (CaCl2) in saline in dogs over a one year period. Five concentrations (0%, 10%, 20%, 30%, 60%) of CaCl2 in saline were administered via intratesticular injection to groups of 10 dogs each. Total sperm count and motility, blood levels of testosterone, and side effects were examined at 0, 2, 6, and 12 months post-injection (PI). Testicular size and semen volume were examined at 0 and 12 months PI. Results: Total sperm count, semen volume and testosterone showed significant dose-dependent decreases upon treatment with 10%-60% CaCl2 compared with either the control group (0% CaCl2) or baseline for each treatment group. Azoospermia was achieved for at least 12 months PI in 60% and 80% of treated dogs after administration of a 10% and 20% CaCl2, respectively. Treatment with 30% or 60% CaCl2 resulted in azoospermia in 100% of dogs, but more side effects were observed, while no side effects were noticed at lower doses. For each treatment group, testosterone levels had decreased an average of 35%-70% at 6 months following treatment. However, testosterone levels rebounded by the 12-month time point in all groups except the highest dosage group (60% CaCl2), which remained at the low end of physiological range throughout the study. Sperm motility dropped to zero or near zero in all dogs treated with CaCl2. Testicular size was significantly smaller at 12 months PI for all groups when compared to baseline. Conclusions: This first long-term study confirms reports of the efficacy of CaCl2 sterilization. However, at dosages free of adverse events, calcium chloride in saline may not provide permanent sterilization as previously believed. Future work should explore optimized solvents to increase the permanence of the well-tolerated 20% formulation. - Background Canine overpopulation is an intractable problem globally despite local efforts to control population growth. In many developing countries, free-roaming dogs cause serious health and welfare problems with resulting socio-economic, ecological, political, and ethical issues. Therefore, the development of effective fertility control measures is a high priority. Many communities that aspire to mass surgical sterilization find it prohibitively resource-intensive. As a result, lifelong housing in shelters or mass euthanasia campaigns continue to be used to control dog populations, but the effects prove to be minor, not cost-effective, and often against international animal welfare regulations [1,2]. Thus, several alternatives to surgical sterilization have been explored. For contraception of stray male dogs, desirable methods need to be permanently effective, minimally invasive, simple, rapid, and inexpensive, with potential for adoption in large-scale animal birth control programs [3]. Intratesticular injection of chemicals is a non-surgical method for contraception of male dogs [4]. This approach has been investigated for more than five decades [5]. An ideal chemical sterilizing agent for stray dogs would be one that effectively arrests spermatogenesis, androgenesis, and libido, while lacking toxicity and serious side effects [6]. Many compounds have been studied (e.g., glycerol, zinc compounds, and chlorhexidine) [6-10]. While many potential candidates possess some anti-spermatogenic or anti-fertilizing activity, most compounds do not eliminate gonadal sources of testosterone [4]. In contrast, calcium chloride dihydrate (CaCl2), a salt used for several medical purposes [11], represents a promising chemical sterilant [12,13]. CaCl2 can be dissolved in water [12,13], in alcohol [12,13], or lidocaine solution [2,14,15]. Several investigators [2,14] have reported that a single, bilateral, intratesticular injection of CaCl2 solution resulted in induction of permanent (i.e., irreversible) chemosterilization, including cessation of sperm production and decreased testosterone in male dogs. These earlier studies evaluated the effectiveness of CaCl2 on testicular histology within two months of injection, and the concentration of sterilant used per testicle was frequently correlated with the animal body weight [2,12-14]. However, use of a concentration per body weight approach is not practical for application in the field, as stray or (...truncated)