A new Spotted fever was seen in 2018 and 2019 in the United States in 3 dogs which had fever and hematological abnormalities; blood samples contained Rickettsia reactive antibody and Rickettsia DNA sequences by PCR amplification. These dogs came from 3 separate states: Tennessee, Illinois (signs developed 3 days after returning from a tick-infested area in Arkansas), and Oklahoma. The tickborne Rickettsia parkeri, R. philipii (Rickettsia 364D), and R. rickettsii cause Rocky Mountain spotted fever (RMSF), human spotted fever group (SFG) rickettsioses (mortality as high as 30% without treatment, but historically, a death rate as high as 80%; however, with doxycycline treatment, that rate drops to 0.5 %). R. rickettsii is the only known cause of SFG rickettsiosis in dogs. SFG Rickettsia seroprevalence is high in dogs in the United States and Mexico. In this study, they examined 3 genes (gltA, htrA, and ompA) and 2 intergenic spacer regions (23S-5S and mmpA-purC) in Rickettsia sp. by PCR. These targetted genes of Rickettsia were 100% identical in the 3 dogs. Multilocus genetic analysis placed this new Rickettsia sp. in a clade among SFG Rickettsia between human pathogens R. heilongjiangensis and R. massiliae. They failed to culture and isolate the new Rickettsia sp. from whole blood. The tick species, in these cases, were not identified, but ticks common to the states involved include Amblyomma americanum, Dermacentor variabilis, and Rhipicephalus sanguineus sensu lato, all of which are known to transmit Rickettsia. Haemophysalis longicornis, an invasive tick species recently found in the United States, including in Tennessee and Arkansas, may also be a possible vector of Rickettsia spp. Wilson JM, Breitschwerdt EB, Juhasz NB, Marr HS, de Brito Galvão JF, Pratt CL, et al. Novel Rickettsia species infecting dogs, United States. Emerg Infect Dis. 2020 Dec. https://doi.org/10.3201/eid2612.200272. The appearance of a new tick-borne spotted fever in dogs should not be unexpected; we have seen this before.
Flinders Island Spotted Fever, caused by Rickettsia honei, first discovered on Flinders Island Australia, is transmitted by Aponomma hydrosauri (a reptile-associated tick, now Bothriocroton hydrosauri). It was first identified on Flinders Island in 1991 by Dr Robert Stewart, who suspected the clinical symptoms of his human patients indicated a rickettsial infection. Symptoms included fever, headache, myalgia, a mild cough, and a maculopapular rash. Serological analysis, including the Weil-Felix agglutination and rickettsial-specific immunofluorescence tests, indicated a member of the Spotted Fever Group (SFG) was responsible for the disease. The reptilian vertebrate hosts for the tick on Flinders Island are tiger snakes (Notechis scutatus), copperhead snakes (Austrelaps superbus), and blue tongue lizards (Tiliqua nigrolutea). In 1998, a similar, if not identical, rickettsia was found in ticks in South Texas. In 2008, our entomologists at Brooks, also found the rickettsia in Amblyomma cajennense ticks co-infected with Coxiella burnetii (Q Fever). R. honei has been found in Ixodes and Rhipicephalus ticks in Asia and in Amblyomma cajennense, as we observed, in North America. Its worldwide spread is hard to explain.
A Spotted fever type Rickettsia from Ghana, West Africa, entered the US in ticks and imported snakes through Florida in 2002. The disease was associated with the Gulf Coast Tick, Amblyomma maculatum, introduced into a snake collection after importation, and the imported Snake Tick Aponomma latum, on the premises. The latter is the most common tick parasite of large snakes in most of sub-Saharan Africa and in the pet trade worldwide. It frequently arrives in the USA on imported pet pythons especially from West African countries such as Ghana. After many snakes died, the outbreak was finally stopped by tick control on the snakes and premises and tetracycline treatment of snakes in prodromal or asymptomatic phases of the disease (otherwise it was 100% lethal after neurological signs appeared even with treatment). Its responses to tetracycline and our inability to consistently culture any free-living microbes from the blood and tissues of acute cases supported it being a Rickettsia or Ehrlichia. Various Rickettsia, Ehrlichia ruminantium (cause of Heartwater), and Orientia tsutsugamushi (cause of Scrub Typhus) target vascular endothelium (Heartwater especially targets brain endothelium) as their main tissue to be infected as did Viper Plague. It was isolated, by blind passage for 4 years, from the livers of snakes, and cultured and isolated in snake and turtle cell lines, and then, the isolates were used to infect various other mammalian cell lines, including mouse, human, and bovine. Because of clinical signs of accumulated peritoneal straw-colored fluid, pneumonitis, gastroenteritis, neurological signs, seizures and sudden death as well as a positive PCR for the genetic marker, it was assumed to be an aberrant Heartwater. The putative causative agent was isolated in viper cells and propagated in turtle cells, but also infected bovine endothelial cells, and human cells (HeLa) as well.






The Heartwater agent is of such concern that it is forbidden, even for research purposes, to be maintained on the US mainland. Snakes belonging to Viperid, Colubrid and Elapid families succumbed to this new disease from July 2002-February 2003 in a private collection into which the snakes imported from Africa through Florida were introduced along with the ticks they carried. However, in spite of being intermingled in the collection, no western diamond-backed rattlesnakes (Crotalus atrox) showed signs of infection or died. This agent(s) may have already appeared in the US as a zoonosis combined with or diagnosed as Q Fever (MMWR, September 1, 1978, V o l. 27, No. 3, 5 May 25, 1978, New York State, the Suffolk County Department of Health Services). During this 1978 outbreak, a total of 11 persons became symptomatic. All were involved in unpacking and de-ticking (Amblyomma nuttalli, Aponomma latum, and Aponomma flavomaculatum) or came in contact with a shipment of 500 ball pythons (Python regius), imported on May 3 from Accra, Ghana. The vipers, which were involved with the 2002 outbreak, were shipped to Florida from Ghana along with ball pythons (some may have been co-mingled in transport bags) from the same vendor(s). Characteristic lesions of abundant straw-colored fluid in the common body cavity, inflammation with abundant mucus in the lungs and intestines, and accompanying diarrhea as well as per acute deaths in many cases with little or no signs beforehand were observed. This unknown Rickettsia tested positive with antibody against the OX19 Proteus vulgaris antigen, the same antigen used in the Weil–Felix Test. This test uses antibody against the OX19 antigen of the Gram-negative, free-living bacterium Proteus vulgaris which cross reacts with spotted fever and typhus groups of Rickettsia. It was the first serological test for the diagnosis of these rickettsial diseases (Edmund Weil and Arthur Felix in 1916). As I have already stated, emerging spotted fever group Rickettsia has already been seen as a zoonosis from reptiles, so except for the unusual genetics, this result should not have been a surprise. What was a surprise was that a Rickettsia could have appropriated genetic material from an Ehrlichia, probably co-infecting the same ticks. Species lines in these types of microbes have become very blurred. We were just very lucky that this worked because overall sensitivity can be as low as 33% and specificity as low as 46%.


























































































